Here is an interesting observation.
As you all may or may not know I have converted all my pano gear to use the R1/R10 lens ring mount system. I have a couple of extra upper arms sitting in my spare parts box. My first home made pano head used the ring mount. One of the very first modifications I did to my M1 was to convert it to ring mount.
The settings on the M1 are dialed in for the Nikon 10.5 lens. Last week I purchased a 16mm lens and ring mount. While going through the calibration exercise for the 16mm I discovered that the settings for the 10.5 are within a couple mm of the settings for the 16mm. They are so close that if I split the difference, I do not have to touch a thing when swapping back and forth between the two lenses. We are talking 1 or 2 mm.
Gotta love Nick's ring mount system. Makes swapping equipment so much easier. It also makes pano heads much simpler.