Oh, and back on topic...
It actually looks like the seat was designed so that it could come in two configurations - as it is, and as a single seat with a "boot" The seat has some holes which look like they would accept screws like all the other body work has, but the only thing missing is the correspoding hard-points.

This would allow me to simply cut the seat plastic just in front of where the hooks are located so that the rear portion can act independently of the seat.
So it looks like I need to figure out a way to add some hard-points, or just cut the foam out of the rear portion of the seat and re-upholster it as needed. It would be a lot neater if I do the first...but more trouble. And it would likely require a welder, which I don't have (don't know how to weld either, actually). Anyhow, normally I dream answers to these sorts of problems, so I am off to do some problem solving...ZZzzzzz....