wood coring question

[SkunkBoat]

I have starboard lids inside the cuddy and a starboard cap over the gunnels and I think if they were on deck, where the fuel tank is, they would be trashed.
Great stuff but IMHO not right for that spot.
Also, sealing the hatch would be troublesome since not much sticks(or stays stuck) to starboard. Warping might also be a factor.

Dryply is just sheathing treated for temporary exposure to rain during construction. Not useful for a boat.

PVC sheetboard won't bond with poly resin and probably won't hold epoxy well either.

I know I sound like a downer....

Here are some choices.

Marine grade AB douglas fir ply, $50 for a 1/2"x4x8 sheet at Lowes.(Do NOT use pressure treated pine)
Coosa, $300 for a 1/2"x4x8 sheet...PLUS Shipping.
Seacast or CarbonCore/Arjay/Nidacore pourable.
End grain balsa.
Hexcore or various foam cores.