I use the Kuryakyn version of that same bag and really like it. It can be made to mount on top of the pillion so that it can double as a driver's backrest. Works very well.
If you really need to hang it off the back of the sissy bar, you should really consider a luggage rack. It will help the bag last longer.
If you really need to hang it off the back of the sissy bar, you should really consider a luggage rack. It will help the bag last longer.