Bonding veneer to fiberglass and applying epoxy finish?

[dbhost]

With the camper cabinet rebuild process, I am looking at reducing weight so instead of MDF (99.5 lbs per sheet of 3/4") I am looking at a combination of birch ply (74.4 lbs per sheet of 3/4") and 3/4 XPS foam. 3.9 lbs for 4x8 sheet of 3/4.

Now XPS itself isn't super rugged. So yes I am planning on doing fiberglass, and of course polyester resin eats XPS foam instantly but epoxy doesn't. My thought process here is...

#1. Build the countertops 3/4" Pecan / Hickory and Walnut butcher block.
#2. Build the cabinets / fiberglass them, smooth them out and then APPLY veneer. Once veneer is applied epoxy finish it to protect it from moisture.

As the title says, how could I bond the veneer to the fiberglass? I am thinking possibly the epoxy resin, but that begs the question of how to pull this tight to the fiberglass panels.

Again the idea is mass weight reduction but I want to keep a natrual wood look...

[capncarl]

3m spray adhesive will attach to about anything.
had you thought of using a foam board core between 2 pieces of 1/4” paneling. It gets really strong as a laminated ply, and is much lighter than 3/4” birch plywood.