i had a bit of a diversion, so:

regarding the alpa lens shimming, most of the concept is a red herring, since all you are doing is ensuring that when the lens helicoid is set to the infinity stop, the camera is actually focused at infinity. very important, to be sure, but after that, focus at any intermediate distance is entirely up to how accurately you can estimate that distance (maybe to a few inches, if you are lucky) and then, how accurately you can set the distance scale (and ultimately the image distance) on the helicoid to that number.

Here the arca leads the way with the accurate and fine pitch helicoid, set by working from a chart, I believe. Alpa offers add-on scales with intermediate markings as useful aid.

for example, using a 28mm lens with a subject distance of 10,000mm (10meters or about 33ft)and comparing that to a subject distance of 10.2 meters ( 33ft-8inches)

to give you and idea of the dimensions, the lens to image plane distances are:

inf: 28.000mm

10M (33ft): 28.079mm

10.2M (33ft-8inches): 28.077mm

so at about 33ft, 8" subject distance change means about .002mm distance to sensor change

the Arca has five turns for it's helicoid and my estimate is it moves about 7mm (6mm is what my 120mm lens has to move to get from inf to 2.6M (8ft). that works out to about .004mm movement per degree of rotation and for a 3" dia lens adjustment ring, one degree is about 1/2mm on the barell, or less than 1/32"

it would take 1/2 of one degree for the Arca to focus between 10M and 10.2M with a 28mm lens

for a 43mm lens, about .004mm difference

for a 70mm lens, about .010mm difference between 10 M and 10.2M

for a 120mm lens, about .029mm difference

using 1/f=1/I + 1/O

any discussion?