I just put a Race Products mono tailunit on to a biposto frame. The frame sticks out a bit at the back, but it depends why you're doing it I guess. In my case it was to preserve the original seatc unit it pristine condition while I took the bike on the track, then I change it back after. Some other makes might well be longer though, but you;d be missing the mounting that it is suppsoed to go onto as well. On mine there is a central screw under the seat unit that is not attached to anything on the frame.
Some pictures of it set up for the track day here
http://82.70.86.166/handk/bikes/inde...ll20050325.php [Edited on 4-4-2005 by HW]
Threaded Mode