...Although I believe dual Revolutions should fit. Apparently 2-1 Remus Roxx won't fit with Jesses. I also understand there is a difference between new Jesse brackets and old Jesse brackets, though I don't know when the changeover happened. Mine were made in 2010.
If you go 2-1 for the left side space for aux fuel tank or toolbox, be careful. As far as I know, none of these will fit with Jesse brackets. I made my own:
In retrospect it was a lot of work. A smaller simple cylinder would have been less troublesome but I wanted to maximize the space available, and mimic the oval shape of the Remus on the other side.
There is also some info on that thread from the guy who had trouble fitting Roxx.
I miss the v-twin rumble that some dual pipes can give you ( I had stock pipes so any change is an improvement) but I wouldn't go back from 2-1....it even improved my ~4000 rpm "hunting" to an acceptable level, and I love that all my tools are on the bike all the time. ATTATT?