Mate. Bike looks awesome.

I'm all in on this wheel subject as I have v7'd my v9 (2016 model) and want to put a wire wheel on the back to match the one I've put on the front. In my investigations so far, I believe that the rear wheel spacer set and spindles (parts 2B001956, GU92204220, 2B001310, 2B001279) for the early V9's is the same as the V7 850. From that I deduce the width of the hub section of the wheels and space between swingarms is very close.
I'm wondering if we could swap out the Flexible couplings' hub (part no's 2B001303 and 2B006860R), get new cush drive rubbers then run the new model wheel?
In regard to "The other potential option is to replace the V9’s final drive with one from an E5 bike and use a V7 Special wheel as you suggested. But the part numbers of the pre-E5 V9 driveshaft and the E5 bikes do not match, so perhaps there’s a difference in the driveshaft-side splines" or perhaps it's just the length of the shaft using the same uni joints. I can't find a part number for either bike's uni joints, but my gut tells me that the uni joints will be the same.