If you want to reinforce and strengthen GWS foam, I would highly recommend going the fibreglass route. This thread:
is a good place to start.
I would suggest 0.75oz glass cloth, sealed with water based polyurethane, (not epoxy) for the A-10. A number of coats of the polyurethane would give a very strong surface.
Given the amount of work you will be doing on the A-10, using “real” fiberglass would not be out of line.