easiest friction drive on a jackshaft

HI. I just bought my Schwinn bicycle to make a MB with the 99cc predator engine. I can see most of the build in my mind but the actual drive roller mounted on a jack-shaft has me wondering if my idea is a good one or is there a better solution. My solution would be to weld a washer to the jackshaft with 3-4 bolt holes drilled and a free washer with the same holes. Cut with a holesaw, a number of rubber disks, as mentioned in another thread, and drill corresponding holes like the ones in the washers and bolt them together to make a friction drive for a jackshaft where I can put the engine in the frame where it belongs. I have spent days reading and searching but haven't found any posts with enough detail about the drive roller to find a ready made one or easier one to build.
I made one in the 60s with a couple of seat post clamps around the bottom bar beside the rear wheel on a 20" and some rigging to hold it up. Just a sheave on the engine shaft rubbing against the rear wheel. This was real awkward to ride but fun for a young teenager. Then girls started being fun and I lost interest in these things till now.

Well, it's running. There are some problems with it but I will fix most of those when I tear it down to paint and use thread locker on most of the bolts. No pictures and no safety award for this one. I knocked a gash about 2 1/2 inches in my ankle but I still made a 20 minute ride around and around the neighborhood to get some time on the motor. I just hope it doesn't make a big messy scar cause it ain't bad enough to pay a clinic or anything. Oh well, it won't be the first scar on this old carcass.