The crank pins are an easy press-fit into the drivers, and thankfully, I didn’t need to remove the rear drivers to insert them. Then the connecting rods and the main rods dropped into place with almost no fanfare, except that I need to get a 1.3mm nut driver for 0-80 screws.
Holding my breath, I dropped the engine onto the test track and turned on the power. The Soundtraxx decoder burst into song, supported by that annoying too-loud air compressor. So I tentatively turned the throttle to one, and the little engine crawled majestically down the track!
No tweaking, no fine tuning, no chasing perfect running quality for a month and never really getting there. Just perfect on the first go. This is the power of the keyed axles. I’m sold, and can see the path forward for #622 and #10 now.
Pembroke:87 
Congratulations on a big success story for your home brew drivers! Its great to hear that all of the effort you have put into this might bring #622 and #10 into heavy service on the Canada Atlantic!
I’m hoping you put together all the experimental conclusions, rejected considerations, and practical fixes into a step by step guide for other modellers to follow.
Thanks Rob. I think there is a magazine article in this one, yup.
Congrats
AH
Thanks!