I have a 1988 seswirl sable. The wood under the fiberglass is rotten. My intent is to remove the rotten wood leaving the fiberglass shell and putting 3/4 inch marine plywood on top of the fiberglass shell. I am going to prep the wood with KILZ first, screw the ne wood down and either fiberglass over it and paint with rough surface deck coat or just use the deck coat on top of the wood. Any suggestions on how I can improve what I am doing??