Thanks, Victor, for the helpful description and photos.

Re: "just spin it": I've finally had the chance to ride it. (Don't laugh, I'm in Vermont, it snowed yesterday!) 9 miles with moderate hills. Found the gearing range does not go as far down as I'd like for climbing, while the top gear or two I would never use. Of course, with a shaft drive you can't change the gearing. I suppose the Dynamic Bikes 8-speed models would be better for me. (There are also reportedly two models of the shaft drive, that differ in the gearing, I don't know which one I have?) There was occasional slippage in the drive train but I think it's the hub (shifter adjustment), not the shaft. I did adjust to align the colored dots (in 4th gear), but in the real world it seems like I had to loosen up the shifter cable just a bit to make it work better. The friction in the drive train is small relative to the pedaling force most of the time. I could feel the "whirrr" when climbing, and hear it only when climbing slowly in a very quiet area. Overall, worked OK, wish it was lighter and had a lower gear.