I also have built an oven the size you are thinking. Just a couple of thoughts after using mine for the past year. You mentioned about gage of steel inside of oven. Be careful and not go to thin as I've had problem's with expanding and contracting. It was causing dust particles (I think from the insulation) to be scattered in my curring powder. Used several seam sealers and they all got brittle and cracked and I was right back where I started. I think I finally have that problem solved. Mine is 28 gage, way to thin, but is okay for now.
Also, the casters you are looking at, what is the load capacity? I have some heavy duty, as my oven is quite heavy, once you get it all together. Got my wheels from HF.
I have ran across a bumper that made me wish I had built a 7 ft high oven. Mine has 2 inch walls and it just fit inside to cure. 7 ft would have been better.
I also have my k type thermo inside a pipe with a cap on the end to read temp and it runs pretty close to the temp of parts for cure times. I have 8150 watts and it takes around 30 minutes to heat, unless it's heavy/thick parts.
Hope this added info helps out as with the other guys. Lot to mull over.
