Here she is with the $$$ foam from the hobby supply store, stuck to the tin backing with contact spray on glue/cement. I just cut the foam out rough at this point. I should of left myself a 1/2" less than I did around the outside. I'll have to remove that much to give the joint compound room to be spread on. First time is always a learning experience.
Here's a view of the wood runners I made this morning that set the seats profile. If I had gone with the styrene foam, I would of just had to carve it to the proper profile. I like this better. Less room for sculptor error.
Now to let the contact cement set up on the runners. I also have some screws holding it all together. I'll start carving the basic shape out of the foam tonight! Hope I get a chance to spread on the first coat of joint compound tonight as well. I should probably be using something harder than the joint compound to form the outside shape, but it sands easy. The plug only has to last long enough for me to make the mold. Once the mold is made, I make the seat pattern out of glass, and can always make more molds as needed from my master pattern.