I like the idea of the pvc, its quick and easy, but I think I'm going to go for the hardwood idea. I'm going to laminate it first in a coat of glass, then shove it in there, build up some glass on top of that, then putsome of that "great stuff" foam on top of that, replace the pumpkin lid and tape it down, so that the foam is forced out of the edges of the lid... then use some kind of marinetex time stuff to fill in the gap. Then it's time for painting.

This sound like a good plan?

(this plan was conceived by my father and I. The former having a couple years of powerboat fiberglass experience, the latter a prodigy in the works :P )