I can understand the difficulty you face, if the proper material is not available. Would your supplier be willing to put a few sheets of marine ply on his next shipment of material, and perhaps split the freight with you?
Whatever you use, I would echo the others and say use the best you can get your hands on. It isn't an easy job to begin with, and it would be a shame to see first class labor with second rate materials.
From my own expierience I would advise that once the piece is cut and test fit that you seal all the edges with thickened epoxy, two coats is best, and then tab to the hull well. Your bulkheads may never have rotted if the edges were sealed well. Wooden boats can funcion well indefinately with water inside, but plywood fairs poorly to being even damp for long periods.
Do the job well and be pleased with the result.
Last edited by feetup; 05-06-2008 at 12:35 PM.
Reason: corected spelling