After you get the multi layers saturated (and cured?), take some 3/8 hose, cut it in half lengthwise, lay it in a grid pattern on the back of the seat mold while it's still on the prototype seat, and lay a couple of layers of fiberglass strips on to form ribs that backup the form for strength. This should give a strong tool that will last forever. Maybe you could sell some seats.

For shapes that enclose the mold / prototype, make parts in two halves (upper / lower) and join w/ some method.

> Projected attempt #3: I think I'll try this for a multi-use seat mold. It
> starts the same as #2, but instead of using foam, just use a few more
> layers of cloth/epoxy. It will be flexible enough to remove from the seat,
> but won't be so flexible that it puckers and dents with a small push. I
> think that should make a good mold.