Min

I would put some spar in the recipe plus some 200 mesh silica. Although, if this is a one time firing and you haven't tested a woodfire body before I would be inclined to purchase a claybody and wedge in your inclusions. I would ask the people firing the kiln which claybody they recommend and if they are okay with you adding decomposed granite or whatever you are thinking of adding that isn't an organic material.

I would put some spar in the recipe plus some 200 mesh silica. Although, if this is a one time firing and you haven't tested a woodfire body before I would be inclined to purchase a claybody and wedge in your inclusions. I would ask the people firing the kiln which claybody they recommend and if they are okay with you adding decomposed granite or whatever you are thinking of adding that isn't an organic material.

I would put some spar in the recipe plus some 200 mesh silica. Although, if this is a one time firing and you haven't tested a woodfire body before I would be inclined to purchase a claybody and wedge in your inclusions. I would ask the people firing the kiln which claybody they recommend and if they are okay with you adding decomposed granite or whatever you are thinking of adding that isn't an organic material.

Katz himself might have thrown a wrench in the works in regards to his testing into flux ratios, also into further exploration into silica:alumina flux ratios. From his 2016 NCECA presentation taken from this pdf.

Hi and welcome to the forum.
Couple things, Mayco Stroke and Coat is a highly pigmented glaze, you don't need to brush a clear glaze on top. Second thing is Mayco recommends a minimum firing of cone 04.
Could you post a picture of the problem tiles? Might help clarify what is going on.

I think we are talking 'past each other'.  I'm not dismissing flux ratio.  As you say, Matt's research shows it to be important. But, it was not the problem with the original question/recipe that started this thread. The original question and recipe had a good flux ratio, so I did not comment on it.  What the recipe does have is a high boron level. That is why I commented on the boron level and not the flux ratio. I think we are in agreement and just suffering from the back-and-forth inherent in using the internet.

Hi and welcome to the forum.
Couple things, Mayco Stroke and Coat is a highly pigmented glaze, you don't need to brush a clear glaze on top. Second thing is Mayco recommends a minimum firing of cone 04.
Could you post a picture of the problem tiles? Might help clarify what is going on.

Okay, using Laguna analysis not the Jeff Zamek 2011 article analysis (plus subbing Fabi Talc) I came up with the third recipe below. @GEP, I would confirm with Laguna that info is still correct.
Second recipe is a 1 to 1 swap of both Cornwall sub and Fabi Talc, it needed some tweaking. Laguna Cornwall sub is up but not by nearly as much as with the Zamek analysis, silica is up and the rest just minor tweaks. Again the sodium + potassium is a combined value.
I think Callie brought up a very important aspect, if Laguna is using Custer spar as part of the Cornwall sub blend then this could throw a wrench in the works going forward. Don't know if they use it or not, anybody's guess at this point. 
To keep this from getting too confusing I'll add a PV version in a separate post.

Plastic Vitrox (PV) version of GB1 using Fabi Talc. (why do I keep thinking that as Fabio talc? lol)
I know PV can vary a fair bit but went with Insight analysis.
Had to supply the calcium from calcium carb in place of wollastonite as the silica was too high using the latter. 

Three recipes below, original in the first one using Amtalc since a specific one wasn't specified. Second recipe shows what the formula would look like just doing a direct substitute of Cornwall Stone for the G200 and Fabi talc for the Amtalc. Third recipe is one where the oxides are as balanced as I can get them without adding another material.
Only change to formula in recipe 3 is potassium and sodium amounts are different when looked at separately but equivalent when looked at when the two oxides are combined. (KnaO figure) Given you are testing this for your liner I don't think this will make a difference.
Main difference is far more Cornwall is needed to supply the sodium and potassium than the G200 supplied. This extra Cornwall bumped the overall silica up so that needed to be reduced by subtracting silica. Same for alumina hence the small drop in EPK. Other oxides just needed minor tweaking.
Silica to alumina ratio is the same in 3rd version, COE is pretty close, this will be a minor fraction of a decimal difference, not significant.
I left the total for recipe 3 at 99.30 to keep the material amounts in whole numbers or just going into the tenths.
If you try this please just do a small test amount first, what looks good on paper doesn't always translate to the pot.

It's the grinding down of the blank going around the curves that I'm wondering about. I think it would be a lot more accurate if I had a jig I could clamp the blank to before grinding it, would help with angle too. There are also ones on aliexpress but I wonder about the quality of those. Hsin-Chuen Lin sells some also, they are all pretty close or the same shape. Makes me question if they are all getting the blanks then sharpening and finishing them. 

So I had decided to buy a sample blank and try grinding the cutting edge so I contacted the supplier I linked above and it turns out shipping is $25-. I don't think it's worth $50- USD for an experiment so I cancelled the order. 
I did go ahead and order the one below from Aliexpress. (4 styles available) Given there are not a lot of suppliers and the styles are the same or very similar I thought it was worth a try. I'll do a follow up here once it arrives and I have a chance to try it out. (no affiliation with either company)

Three recipes below, original in the first one using Amtalc since a specific one wasn't specified. Second recipe shows what the formula would look like just doing a direct substitute of Cornwall Stone for the G200 and Fabi talc for the Amtalc. Third recipe is one where the oxides are as balanced as I can get them without adding another material.
Only change to formula in recipe 3 is potassium and sodium amounts are different when looked at separately but equivalent when looked at when the two oxides are combined. (KnaO figure) Given you are testing this for your liner I don't think this will make a difference.
Main difference is far more Cornwall is needed to supply the sodium and potassium than the G200 supplied. This extra Cornwall bumped the overall silica up so that needed to be reduced by subtracting silica. Same for alumina hence the small drop in EPK. Other oxides just needed minor tweaking.
Silica to alumina ratio is the same in 3rd version, COE is pretty close, this will be a minor fraction of a decimal difference, not significant.
I left the total for recipe 3 at 99.30 to keep the material amounts in whole numbers or just going into the tenths.
If you try this please just do a small test amount first, what looks good on paper doesn't always translate to the pot.

Recent post discussing tungsten trimming tool got me thinking of the cost of these as I'm finally ready to break down and buy one. I did some research and found there are a few suppliers who sell blanks in the shape of trimming tool heads commonly seen for sale by a few ceramic suppliers / artists. (link below)  I read up on how to sharpen tungsten carbide and either a diamond wheel or  a green silicon carbide grinding wheel can be used, along with diamond files for fine sharpening. (we have a green silicon carbide grinding wheel) Most places that sell the blanks are wholesale orders only but there are places that sell samples of one piece. One supplier below who sells sample blank pieces for $25- US each. I can see how to get the outside bevel ground down using a diamond or silicon carbide grinding wheel but not the inside bevel, maybe a diamond bit on a Dremel for the inside angle? 
Anybody resharpen their own tungsten tools? Does that work well?
I know I can just go out and buy one (for a lot more money) but ....
Anybody done this? Thoughts?
https://ostoncarbide.en.made-in-china.com/product/SxoUhujFAVWA/China-Hard-Metal-Ceramic-Clay-Trimmer-Tungsten-Carbide-Pottery-Scraper.html

Plastic Vitrox (PV) version of GB1 using Fabi Talc. (why do I keep thinking that as Fabio talc? lol)
I know PV can vary a fair bit but went with Insight analysis.
Had to supply the calcium from calcium carb in place of wollastonite as the silica was too high using the latter. 

Okay, using Laguna analysis not the Jeff Zamek 2011 article analysis (plus subbing Fabi Talc) I came up with the third recipe below. @GEP, I would confirm with Laguna that info is still correct.
Second recipe is a 1 to 1 swap of both Cornwall sub and Fabi Talc, it needed some tweaking. Laguna Cornwall sub is up but not by nearly as much as with the Zamek analysis, silica is up and the rest just minor tweaks. Again the sodium + potassium is a combined value.
I think Callie brought up a very important aspect, if Laguna is using Custer spar as part of the Cornwall sub blend then this could throw a wrench in the works going forward. Don't know if they use it or not, anybody's guess at this point. 
To keep this from getting too confusing I'll add a PV version in a separate post.

Thanks for the link Mark, the analysis is different for the Laguna blended Cornwall substitute. This could make a difference!
@GEP, I'll redo the recipe using the Laguna analysis. I'll run it with PV also since you have that available too.

Recent post discussing tungsten trimming tool got me thinking of the cost of these as I'm finally ready to break down and buy one. I did some research and found there are a few suppliers who sell blanks in the shape of trimming tool heads commonly seen for sale by a few ceramic suppliers / artists. (link below)  I read up on how to sharpen tungsten carbide and either a diamond wheel or  a green silicon carbide grinding wheel can be used, along with diamond files for fine sharpening. (we have a green silicon carbide grinding wheel) Most places that sell the blanks are wholesale orders only but there are places that sell samples of one piece. One supplier below who sells sample blank pieces for $25- US each. I can see how to get the outside bevel ground down using a diamond or silicon carbide grinding wheel but not the inside bevel, maybe a diamond bit on a Dremel for the inside angle? 
Anybody resharpen their own tungsten tools? Does that work well?
I know I can just go out and buy one (for a lot more money) but ....
Anybody done this? Thoughts?
https://ostoncarbide.en.made-in-china.com/product/SxoUhujFAVWA/China-Hard-Metal-Ceramic-Clay-Trimmer-Tungsten-Carbide-Pottery-Scraper.html

Three recipes below, original in the first one using Amtalc since a specific one wasn't specified. Second recipe shows what the formula would look like just doing a direct substitute of Cornwall Stone for the G200 and Fabi talc for the Amtalc. Third recipe is one where the oxides are as balanced as I can get them without adding another material.
Only change to formula in recipe 3 is potassium and sodium amounts are different when looked at separately but equivalent when looked at when the two oxides are combined. (KnaO figure) Given you are testing this for your liner I don't think this will make a difference.
Main difference is far more Cornwall is needed to supply the sodium and potassium than the G200 supplied. This extra Cornwall bumped the overall silica up so that needed to be reduced by subtracting silica. Same for alumina hence the small drop in EPK. Other oxides just needed minor tweaking.
Silica to alumina ratio is the same in 3rd version, COE is pretty close, this will be a minor fraction of a decimal difference, not significant.
I left the total for recipe 3 at 99.30 to keep the material amounts in whole numbers or just going into the tenths.
If you try this please just do a small test amount first, what looks good on paper doesn't always translate to the pot.

@Kelly in AK +1 about inside and outside profile and thickness.
@Griffithpotteryworks, stick a couple thumbtacks into the pot from the inside at the midway point plus near the bottom of the side wall then trim down until you reach them. Remove the tacks then smooth over the holes they made. It's a good way to get a feel for how much clay can be taken off. Tap the pots as you trim them so you can hear how the clay sounds as it gets thinner then after a few pots you won't need the tacks.

If any of the glazes needs a slow cool to get the desired look of the glaze then no, I would not use a faster schedule. If all the glazes are fine and look the same with the kiln just doing a free fall then yes it would be okay. You might find refiring them causes the glazes to be a bit overfired if going to cone 6 as they have already had some heatwork. If in doubt I would include one pot in the next firing and see what happens.
Bigger issue would be why the bottom shelf is underfiring.  Is this a kiln with a single thermocouple in the middle of the kiln? If so then going forward pack less mass in the bottom of the kiln, ie taller pots on the bottom, more density (short pots and more shelves) in the middle of the kiln. If it's a 3 zone kiln then I'ld be looking at doing a tc offset for the bottom thermocouple.

So I did get a small update from him on facebook, or at least a response. It did not say anything so that was not helpful but at least he is seemingly ok and checking facebook. I think he just gave up on his emails. I responded kindly and never heard a word back so we shall see. 

Hello Hotzn,
Welcome to the Forum. 
Your questions are a bit too technical for easy answers. You would really need to decide which clay you want to use and then run your own tests to determine "draft angle". ("Draft angle" = the taper necessary to allow for one piece to be pulled from another.) 
Different clay bodies have different levels of shrinkage. I'm not sure which would be more advantageous for you, clay bodies with lots of shrinkage or clay bodies with less. Those factors then affect how easy the body is to keep in suspension. (On a consistent basis.) 
Years ago 3M had an Industrial Ceramics division and they commissioned me to make a simple mold for a simple piece.(For engine cylinder liners.)  We never got into clay formula discussions. Years later, when I reached out to my contact to ask a technical question, I learned that he had retired and that they sold the division to a company in Mexico.
More recently another local company, a branch of a Dannish company, approached me about making molds for silicone carbide kiln furniture. That project never got off the ground but they did show me the process for making another ceramic product they made. (Deisel engine air filters.) The "clay" was black and made with silicone carbide powder. They extruded the forms in a very precise extruder device. They fired it, however, in a nitrogen fueled "kiln" and fired them to 3000 degrees. Thats what I envision you're looking for but that's super technical stuff and I have no idea how where you'd begin on that.
Good luck.
 

@Kelly in AK +1 about inside and outside profile and thickness.
@Griffithpotteryworks, stick a couple thumbtacks into the pot from the inside at the midway point plus near the bottom of the side wall then trim down until you reach them. Remove the tacks then smooth over the holes they made. It's a good way to get a feel for how much clay can be taken off. Tap the pots as you trim them so you can hear how the clay sounds as it gets thinner then after a few pots you won't need the tacks.

I know you said the pots were dried for several weeks and they were candled but when looking at the images this looks like a blowout from an air pocket that contained moisture within. This isn't the same as an air bubble.
My hunch is that when you were centering and opening up the mass of clay there was some clay pushed down that overlapped the existing clay and formed a pocket. If the clay contains a fair amount of ball clay or other fine particle material and was also heavily ribbed over this would exacerbate the problem of allowing the moisture to escape. Think about a fully enclosed form, yes we can fire them without them exploding or having blowouts but it takes far longer for them to reach a bone dry state right the way through the clay wall than the same form with an opening in it. No clue what the weather and humidity is like in Northwest Arkansas, perhaps it's a contributing factor, don't know.