I have thought about this in the past, discussed it with Roger back then and did some research.
In my opinion the main problem is the width of the belt. With only space for a very narrow belt on the drive side of the flywheel you would have to have a very narrow but strong belt. I have checked with several belt makers but those are hard to find (for the horepower and rpm needed). Most belt conversions (Norton, Thriumph etc.) use rather beefy belts and rims!
Especially if you would like to use a self tracking belt (like the eagle pd from goodyear) to avoid the use of flanges (that take away even more space from the actual belt width). The one that came most near was offered to me at 700 euro’s… Well, I do like some experimenting but this simpy was to much!
So, for me I will stuck with my beltconverion for driving the magneto or dynamo and a chain for the primary.
But, maybe others think otherwise! And maybe Roger has done some more thinking on this in between.