> I'm not sure exactly what you are proposing. I wouldn't worry too much
> about the shrinking seat though. First, it's very easy to remove small (or
> large)amounts of foam with an abrasive. Second, when you sit on a flat
> surface, your rear tries to flatten as much as possible, whereas the whole
> point of making a custom seat is to spread your weight as evenly as
> possible over the greatest surface area possible, so a bit of build-up on
> the sides particularly will pay dividends.

What I was getting at was - hopping in the foam, letting it set up, getting out(!), shaping the result a tiny bit, placing saran wrap or vaseline all over, putting in spray foam where you sat, throwing away the first step and glassing over the second. Same as with the sand, but use foam for a good fit.

Idea anyway?

-mike