While it would have been interesting to analyze and break down the rest of your post , this little bit is my favorite:
If you are shooting hand held, with a rangefinder, you will have moved quite a bit between loading and unloading the polaroid back, then loading the film holder for the polaroid to be any reference for focusing.
If you are working on a tripod, why not just check the focus on the GG before loading in a film holder? It must be cheaper, faster, and far more useful, if you wanted to confirm the focus before shooting actual film.
If the point is to have giveaways or create "rapport", i am not sure how the focus confirmation comes into play, but i am sure yo have your reasons.
Good luck with your mask.
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