Body building polycarboate vacuum forming

[Overdriven]

Most of the 1/4 scale guys make a buck out of foam, either sheets layered up or a couple big chunks. Once they carve it to the general shape, its covered in bondo. This alows for sharper lines and to add detail as well as smooth the foam. The buck is then painted for a smooth, non porous surface and used to make a mold for the final body which is usually fiberglass. But they aren't exactly concerned with weight most of the time either in 1/4 scale machines.

It may sound bizarre, but what about concrete? I'd think that it could be used to fill the buck and be plenty strong to withstand the pressure of vacuum forming lexan. I think concrete with a layer of clay on it would be less likely to crack than solid clay. I'm just talking out loud here btw, throwing out ideas