At long last, I was able to finish installing the new drivetrain, this time on the left foot.
As I was testing on the carpet, I ran R2 backwards and forgot that I had removed the wedges that keep the feet from pivoting. That caused the back of the center foot shell to get wedged into the carpet and develop a partial crack on a seam that will be easy to repair. It didn't even break the seam all the way, and the shell is still very solid. The hard part will be getting the center foot off, as the ankle bolt hole is crammed in there pretty good. It can wait for a little while.
Anyway, R2 is running great with the new drivetrains on the feet, at least for the few minutes I could run him in the confined space of my home.
Thanks again to Mike Senna for not only coming up with the drivetrain design, but for all the work and help he provided to make the drives a reality.