Is it the seat that's out or the termi's?
The seat is only held in by four bolts, two on the sides and two underneath, I don't know about yours but my R can have the seat/tank etc in 3 different positions via the side bolts, the underside ones just locate in a slot, maybe just undo them and push/pull the seat until it's correct.
But it could be the pipes that are out, did the subframe get bent in your off?