I awoke this morning with a fresher mind and realized that
all I need to do is determine the flange to film distance
when the rear element strikes the shutter plate.

As measured this morning, from the front of the shutter plate
to the film plane is 2.52". From the lens flange to the back
of its rear element is .63".

This gives 3.15" as the minimum available flange to film
distance (before the lens hits the shutter plate).

Based on my earlier measurements which gave 3.12" as the
flange to film distance when focused at 23m, I'll say I won't
be able to achieve infinity focus without shortening the
lenses. I will, however, be able to focus at 2.8m with .02"
of lens clearance.
________________________________________
John Thurston
Juneau, Alaska
http://stereo.thurstons.us