If anybody was wondering how this project went, well, I would say not the best! After a few firings a crack started to appear across the middle. Then the guy who I used to share the studio with (now left after many problems) decided to put another loose layer of bricks on top while I was away and helped the crack go all the way through the brick.
What was my mistake?
I assumed the kiln cement would arrive at the right consistency to get on with.
I tried my best to research but I never read anywhere about watering down the cement until I bought Olsen's kiln book. I should have bought it before starting this project... Looking back at the Pargon kiln video their cement was a lot more fluid and I should have noticed
Lots of the joins ended up being 5mm instead of the recommended 1mm. Mixing up the cement into a thinner consistency would, I think, have given me much better results.
In the end I am selling this piece of ... and buying myself a shiny new kiln so I can stress out about more important things. Still it has taught me a lot battling with it to make it work properly.