Feet

I drove down to my dad's workshop a couple of times before work this week and made still more progress. On Wednesday, we took a look at the foot shells. The foot drives seem to work, but the motor mounts are lower and farther back than the hemisphere in the center of the outer foot. Now, the motors project from the motor mounts, and we want to use the hemisphere cutout to conceal the motor. Because of the position, however, we're going to set the hemisphere back in the foot shell and make the foot shell a bit higher than is "correct."
This difference will be obvious to anyone who has studied the structure of R2 well enough to try to build him, but it probably won't be obvious to anyone else. In either case, and in the spirit of George Lucas' endless backstories, here's the rationale: This R2 unit has foot shells and foot drives that indeed deviate from the norm. R2 is a modular droid, after all, and these particular modules would have been changed at some point.
Ha! Take that, pedants!