To use the mid 90's Virago short riser you must already have the standard backrest assembly. You'll need to sand down some of the ends where it nests into the side rails so it will let the bolts line up. If you look closely you'll see the casting line where the factory used it to help them do that trimming.
We also make a modified Virago riser with a pad for a nice look that is still functional.
Alternatively, you can weld on the Virago riser to the stock grabrail with some modifcations to both. I've only done that a couple of times but it looks pretty cool too.
The HAC backrest is a quick removal design that still sits similar height to the OEM backrest but keeps the stock grabrail (it requires the removal of the reflector which is where those bolts attach). I have one of these (with the optional rack).