Although i don't have a huge extence of experience with fiberglass i have worked with it quite often and i know a few facts about it.

1. if someone has a mould (ie profesional hardtop makers) it will always be a lot cheaper for them to makethe product than you.

2. the idea of constructing a frame is a good one BUT you would need to cover it with a thin plywood as the stocking material would sag. although it does works for speaker pods.

3. the 'lay up' of the fiber glass is easy getting the mold perfect is hard.

i have though alot about making a fiberglass hardtop for my ute and it aslways ends up that it will cost to much. In glass and resin alone you would spend $300. and the prep of the mould would take days. but doing it yourself could be rewarding, and definatly cheaper than $2000.