PVA is water based and would probably bond to, and soak into the masonite. I don't think wax would be enough or apply well over just masonite. Most molds are finished with tooling gel coat($$$) I think something epoxy based might work ok as substitute for this. My thought on mat was mostly price, If you tape the inside seams, and don't add the same thickness of glass to the rest you will end up with ridges or areas that were faired a lot. I suppose cloth will be thinner than mat, but cost more. If you use foam, it will definitly have be covered anyway. Another idea on fillers, you might mix up your own bondo,with a high percentage of microballoons to make a VERY easy sanding filler.

: I wouldn't use matt on the inside; smoothing all that (female) matt surface
: would eat your lunch. How about taking advantage of the smoothness of the
: masonite by applying the release agent directly to the masonite? You'd
: only have to fill and smooth the joints. If you have the materials on
: hand, run some adhesion test.

: Since you have CAD, you could reinforce the mold with an egg crate structure
: mado of female station forms.

: I'v been wanting to do the same mold idea for a compounded plywood design,
: but havn't got it worked out yet.

: Good luck.