Are they sturdy enough to support an average person's full weight on one of them? I'm thinking of the mounting move where the passenger steps on one, and swings their leg over to settle on the seat.
No, you don't want to do that. And there should be no need for it on the little Enertia.
Not that my wife would EVER ride with me (and, ignoring for the moment the fact that we would very likely not fit on the bike without some major re-engineering of the seat), but she's a bit of a midget - only 5'3" - and could not get her leg over the Enertia's seat without standing on a footstool - or a foot peg.
