Why not seal the board all the way around, heck why not wrap it in some tight cloth and soak that baby in resin?

I thought about it. Just seems to me the PVC is less messy to work with.

If I do the board, I have to set up an area to do the glass work... goop it on, let it set, flip the board, glass the other side, and let it set. Then gel coat at least one side. Just seems like a lot of mess, when I can get a single piece of plastic to do the trick.

The question seems to be the adhesion of sealer to the PVC... Which obviously, if that fails, then I've got a mess on the boat. But isn't the FRP of the boat a type of plastic too?