Gene [and MJD], thanks for the link to that supplier and the recommendation for which belt system to use...!
If all else fails, I'll have to scrap the system I built and try this.
Besides cost, the first thing I wonder about is how bulky a twin / divided / siamesed cogged pulley with integral spinner cone will be at the engine. I need to draw a side view of that.
If what I built [so far] wasn't working at all with no promising results I would have scrapped it after the first attempt failed. I've got enough invested in this 2nd attempt [not a lot, but enough] to keep me from scrapping it just yet.
I've got to get the current airframe in the air and get the major kinks worked out. I might as well use a single engine that weighs about the same as the .049 powerplant and clear that hurdle first.
I just received a couple different props to try with the .049 powerplant and will see how much thrust they produce. I've got an assortment of spare O-rings and will experiment with less tension and a floating idler pulley for each belt.
The .049 that I fitted with a front bearing isn't doing so well. I had to undercut the front of the shaft to slide into the bearing. The cut takes the shaft O.D. even with the rut that Cox has near the end of the shaft, so I hoped it wouldn't weaken the shaft too much. I was wrong.
It hasn't broken but it has a wobble. Cox left that extra nub of load bearing steel at the end of the shaft for a good reason I suppose.