Can't really take all the credit. I have a friend who runs a small NC machine shop. He makes really cool stuff, almost all bikes or hot rods or military pieces. He was doing stuff for Eric Buell's racers (remember that guy?) before the fall. Several Victory Motorcycle parts for the Cop conversions. Would you believe a sidestand on EACH side of the bike? Hm: now that I think about that, I see a pattern; not sure what it means though...
I came up with the concept, and he figures out how to make it work. The key was locking the adapter to the splined piece, which prevents sprocket torsion from trying to twist the adapter off. We used Class 12.9 M10 bolts to lock the package together, replacing the short, pressed-in bolts that held the spline fitting to the wheel. I was bummed because I could not find M10/12.9 is anything other than black oxide. "No sweat" said Rob. Just took them over to his friend the plater, and the next day they were yellow zinc! Also his idea to use similar bolts threaded in from the back side for sprocket mounts; there is a solid 1"+ bolt shank thread into the adapter. The reason they are still long is that I don't want to cut until I verify alignment. Then I'll need to get re-plated.
Below is a pic of the wheel with the cush drives visible. The stock spline actually provides support for the bearing boss, which is only about 3/16" thick; so we wanted to make the adapter be able to keep as much of the stock hardware as possible.
That's a stock 34T sprocket, with no problems for clearance - looks like it could even accept a 32 if someone wanted.
If anyone is interested, he is open to making some more. I do not know what the site policy is for defacto "shilling"... but I have no financial interests in any of this. PM me if anyone is interested I guess. This is specifically for an XS1100, with a 17x2.5 wheel. I went with the 17 to provide lots of tire options. Other wheel sizes may be the same isolation/bolt pattern configuration, but I cannot say.