@imamotohead: i used the seatpan from airtech. they're about 15min away, so it was easy to take the carpy seat over (they didn't like that!), & try out their form to make sure it would fit. i dremeled off the wrap around portions of the pan so it was flat and would sit flat on the seat and backrest. pretty easy work. i had to grind off the old seat mount, both helmet hangers, and the old seat lock to get the seat to sit flush on the frame. makes for a bit bumpier ride, but not really bad at all.
as far as the actual mounting goes, i took some advice from other forum members. i put the pan on the seat, put them both on the bike, and lined everything up. you know that flat cross plate just behind the battery box? that's my mounting point. i marked my holes on the bottom of it, drilled it out, marked the holes on the seat, drilled them, and finally marked the holes on the pan and drilled it. took some ss bolts w/ some good sized washers and epoxy'd them to the pan so they wouldn't move. had the pan upholstered, and mounted it all up. it's a little thicker and softer than i'd like, but i was impatient and didn't want to wait for firmer foam. feels like i'm sitting on a pillow
the nice thing is that if i want to reupholster the seatpan, i can just pull it off and not worry about doing anything w/ the expensive carpy seat. hope that helps!