Reply to "foamcore to plywood and to itself"

I would like to be sure you are asking about foamcore (a thin layer of foam sandwiched between cardboard sheets) and not extruded polystyrene, which is an insulation product used in home construction. I use or have used extruded polystyrene--pink or blue color, but normally the pink stuff--on a lot of layouts in various scales, and highly recommend it. It comes in 2" thick 4x8 sheets and is easily cut or carved, leaving no mess, with a hot foam knife (available at hobby shops, craft stores, and from Micro-Mark, among other places). The extruded polystyrene can be glued to a plywood base with Gorilla Glue or several other adhesives available at any home improvement store.