If the foam were in an inflatable pillow (or other closable bag) it might work to make a mold for a fiberglass seat base. Now what we need is a source for expanding flexible foam.

> I don't think it would really work that well. The stuff doesn't
> much like direct impacts, namely from your backside bouncing up and
> down on it in the waves, and it breaks down very rapidly in direct
> sunlight. Glass coating it might work though. As far as forming it,
> the stuff plays weird, it's pretty much either set, or not. So sitting
> on it in a box will most likely result in you sitting on the very
> bottom of the box, with foam squirted out everywhere. I'm not sure
> how one could achieve a good buttocks impression with the stuff. Perhaps
> hanging from something and lowering onself in only part way.

> I don't know if it would really work anyhow. An exact buttocks
> impression would severely limit motion and result in stiffness and
> chaifing. You want some room for moving around a bit to stay comfortable.
> That's why a tractor type saddle works so well. It allows wiggle and
> squirm room.