I'm fixing up this older board, the top shell is delaminating from the bottom and the fin has been screwed in by a metal plate - bolted down lol.

I'm not sure if the board is epoxy or polyethylene etc. What I was looking at doing is removing the rusted metal plate and using polyester resin to fix the holes where the fin was screwed in to stop any water leaking into the foam, I'm not sure of the best way to fix the delaminating problem. Any one know the best way to go. Thanks