The element holder design has definitely changed since the Econo Kiln line was made. I don't know if the brick slot has remained the same, though. You'll have to call L&L on that. If they do fit the same then you can break out the old ones and put in the new ones, or just wait until you're ready for an element change and do it at that time when you can remove the brick and slide them out.
I wouldn't trust cement to hold those element holders at all. Plus you run the risk of getting cement on the elements which would be bad for them. Just replace them. Talk to L&L, though, because the new holders may not fit in the old slots. You may have to replace the entire brick, with new holders.
Marcia- refractory cement does not hold well on old bricks, plus a big part of what makes a lid or floor slab strong is the layout of the bricks- staggered joints. Cementing up a big crack won't have that benefit, so it is very weak. Bite the bullet and replace it. It will have to ship freight, so get a shipping quote before ordering it. I just got a quote for a replacement floor slab for a Skutt 1227 and it's $165 just for shipping. Of course, you'll be a lot closer in Montana so that may help.
If you do it with glazes, then chances are they will run and blur your design. Single firing can also cause problems unless you fire very slowly and/or have glazes that can handle single firing. If I were you I would do the technique with underglazes (won't run), bisque fire, then glaze the whole thing with a clear glaze. Look up 'mishima'.
We used to mix a cone 6 spodumene body at A.R.T. Clay that was a beautiful toasty orange-brown. No matter how well it was mixed we would get variations in color from box to box. I suspect it was also very picky about kiln location, temp, etc. Anyway, most glazes did not fit it very well. It was super tight with a very low shrinkage rate, similar to a flameware body but not to that degree.
Laguna WC-429 does not look like anything special in terms of having spodumene in it, though. It looks like your typical cone 6 brown clay that uses Redart or such for its color. So I, too, would question that low COE.
The biggest problem my students have when moving up to larger amounts of clay is that they don't cone it properly during centering. If you don't bring in the clay at the bottom of the cone enough then that part of the clay does not center up properly, and since it's at the bottom it messes up everything else above it. From a ball of clay to a cone, the diameter at the bottom of the clay should reduce by about half when bringing it up.
Also, when bringing it back down, come down slowly and focus on pushing in at the top with the left hand or you'll be chasing a mushroom all the way down and it will overlap when you reach the bottom, making a mess.
Any time you mix or layer glazes you essentially get a new glaze. You won't know if that new mix is good or not unless you test it. Many combinations are more fluid than either glaze on its own, some bubble, some crawl, but many work just fine. You'll just have to test them to find out.
When dealing with raw glaze materials, you should consider them all to be toxic to some degree. Always wear an appropriate mask, sponge clean, wash hands, don't eat or drink or smoke when handling them, good ventilation, etc.
As for the fired materials, it depends. 3% copper can be perfectly safe, or it can leach out. It all depends on the formula of the glaze. There aren't many hard and fast rules that are always true, so you have to learn to formulate good glazes, and have them tested.
You don't have to have a concrete floor. Just put a layer or two of cement board under the kiln. Not a bad idea to line the walls around the kiln with it, too. You want the kiln to be 16" from the walls.
Sorry I missed your call today Tom. For me the greatest benefit of a digital controller is not having to turn up the kiln. I can start it up and come back 9 hours later to make sure it shut off. I can fire overnight when the heat of the kiln is the greatest benefit or least detriment depending on the time of year. My schedule is crazy so having that freedom is worth a lot to me. If you're only firing on weekends when you're home anyway, then it's not such a big deal. The second benefit for me is getting the same firing and cooling speed from 3 kilns of drastically different size. But if you only have 1 kiln, or kilns of similar size, then that's a non-issue. The third is controlling the cooling/ramp/soaking rates. But if you're firing at low fire temps I don't think you'll get the benefit from that like you would if you were firing to cone 5/6.
When you say the cone wasn't bent properly at peak, was that before or after the hold? The hold will adda lot of heat work. Slow cooling from the peak temperature will also affect heat work. So you either need less hold, a lower peak temp, or add a crash cool from the peak down a couple hundred degrees before you start the slow cooling.