Post-Script: Though I'm optimistic and excited about this project, I'm still working through teething pains. Today for instance I still had some mysterious light leaks/lens flares on my test images. I'll have to do a round of more serious partitioning tests in order to track down the source. There's also the possibility of resorting to using my more modern Fuji 135-f/5.5 lens, in place of the WWII-era Kodak Ektar 127, should the tests point to the lens as (one of) the culprit(s).
This morning's round of tests were in my front courtyard, in bright shade. My test victim again was very patient with this procedure, though she's a bit self-conscious about less-than-flattering images being posted on the Internet for all to see. Regarding her image, I'm pleased with the tones and sharpness, especially considering it was a 3 second exposure at f/32.
Later in the morning I did another test, this time a still-life of my Galaxy 12 typewriter, and I had more mysterious fogging/flares around the edges, which you can see in the bottom and also on the right half of the platen. But the lighting was brighter and more direct; you can just spy one source of bright light being the courtyard wall window, on the upper right corner of the image, just off-axis of the image. I'm certain a properly designed lens shade will improve this situation, if not a newer lens.
Top photo via Fujifilm Instax 210 camera. Typecast via SCM Galaxy 12.