It seems there are lots of ways to do this. I'm new at Comets so this is great to see. By the way, I like the location of the sidestand on the Vibrac Egli. Plenty of support right there between those two through bolts.
For some reason I had a lot of trouble getting the belt on or off when tensioned correctly. I could not quite do a 90 degree twist but was getting the 25mm up and down slack Bob Newby recommends. I may be getting things too tight. Are the pulleys 36 x 68? There is not a lot of belt run between my pulleys to get 90 degrees without a lot of slack.
If you have figured it out.... let me know how long of a side stand you need. I have one off a Honda VFR800 that you are welcome to. It looks like the one above. I ended up using one from a 2000 something Triumph which was slightly longer. The Triumph one has a mounting flange with 3 bolt holes and I mounted it in the same general location as that Egli. I was able to slightly enlarge one of the bolt holes and run a longer lower gearbox mounting bolt through it. Will post a closeup picture when I can.