for foam use the std blue or pink foam that you see in homiedepo or lowe's(you'll probably have to serch a bit just to find 1/2" thick). this useing the epoxie. just fiberglass each side of the sheet and then cut the individual pecies out. assemble them useing pins to hold position. round off the outside edges( maybe 2"radius ) and glass 'em useing fiberglass tape( two layers...first 3", second 4-5") inside mix sawdust, micro spers, flocked cotton fiber, or cab-o-sil - and fillet the inside corners ( about 1.24 radius..when that's almost hardened, apply 3" fiberglass tape to the inside corners. as for a fairing that's got a lot more work involved, and your probably better off trying the more involved mold making. for this use the same type of foam. and finished with plaster or something like it, sand to PERFECTIO once it's done a few coats of paint to fill in the pourus plaster and coat with mold release. then fiberglass away untill it's been built up enought ( insert a few braces too.and two "strong backs" so that once finished you can turn it over and sit it on the strong backs.) then you can fiberglass the final part, if you're lucky enought try to use the vacume bagging technique.