[aerohead]

Are you going to make a male mold (plug) ?,then make a female mold from it ,and then layup your shell in the mold?
If so,once your body bulkheads are established,heavy wire can be used to span the gaps between bulkheads,onto which expanded metal lath can be attached.Then a cement based molding plaster can be applied onto the lath and built up and smoothed to create your plug.
After the plaster is cured it can be sealed with shellac,coated with polyvinyl alcohol mold release agent,and three coats of carnauba wax,before a plaster splash (mold) is created over the plug.
The splash is tooling epoxy followed by birdnests of plaster-soaked hemp fiber built up about 25mm thickness to create the female mold from which you'll make your shell.