My Corbin seat needs refurbishing so I was going to temporarily swap over to the standard Ducati seat, but the tailpieces are actually totally different and the one for the standard seat doesn't fit my bike. These are both 900ss but the standard is from a white frame 1992 model; the Corbin version from a 1995 model. Standard on left, Corbin version on right.
I'm not so sure that you have a Corbin tail piece but rather you have both versions of the Ducati tail piece. I looked into getting a Corbin seat a while back and I'm sure that I read that it only fits the earlier models due to the change in seat fixings. I wonder if somebody has fitter earlier tail bodywork to allow them to use the Corbin seat.
I can shed some light on this as mine is a 93 and my mates is a 92. They both have the tail piece which takes the cross bar fitting the later models changed to a single pin. I have a seat from a later model and a tail piece thinking I could swap but they still don't fit the seats are slightly different. It aligns differently. I do think that my frame geometry is slightly out at the back though due to what appears to be a rear end shunt before my ownership. The change seems to be about 94 onwards as most seats and tail pieces on ebay are the later type. I would try taking the fitting off an earlier seat. The two screws are in the same place. Try that with the earlier tail piece.
