If you are going to be laminating over the wood go with Fir. It is a good dry wood and you get a good bond to it. It is much easier to find then marine grade plywood, which is real hard to find these days. What are you doing with it if I'm not being to nosey? I've got 29 years in the fiberglass industry and most of it building and repairing boats if I can be of assistance please let me know.