I would talk to the guys at "Twisted" and see what they think. I have the Bags Connection "Racepack" for my GT 1000. (The Racepack is the slightly smaller version of the bag you're considering.) The day I bought it I rode my Multi up to pick it up. It didn't fit the pillion seat very well, but I'm not sure that they fit exactly the same.
The quality of the bag is excellent. If you can make it fit. You'll probably be very happy with it.