[macojoe]

What a nightmare!! I am glad you did all that measuring!!

I don't think Starboard is the right stuff. Unless you buy a real thick piece and try to carve it out of that .
The problem with starboard is there is no real good way to glue pieces toghter, it all needs to be screwed tioghter and over time I don';t think it woud stand up.

But if you knew a plastic welder then it might just be the ticket!!

If it was I and I could not find one, or one to borrow, I think I would try to make one out of 1/4 plywood. Get it so it works and it is real tight!!
Then I would cover with non stick stuff, and cover with fiberglass. When dry peal the ply away from the new fiberglass slider, clean fill gelcoat and there you go.

Not trying to say it would be easy by no means!! But that would be the best bet.