[gjbingham]

That steel sounds like a better idea. The weight of the oven is not supported by the walls of the dome alone. As soon as you put insulation under the dome, I believe it will spread the weight of the dome, to some extent, on to the insulation layer inside and outside the actual circumfrence of the dome. In my small mind, I can imagine backer board holding up ceramic insulation board and maybe a layer of brick on the floor. Not much more than that. I've been wrong many times before.