Here is a little cheat-code: If you take a very portable 6x9 medium format camera and put delta 3200 in there, then stand-develop it, well grain is equivalent to APX400 in 35mm yet your dynamic range will be so great your meter will become bullshit.
f3.5 lens? Dark-ass environment? I don't see a problem. And if you accidentally overexpose it and rate it as a 200 ISO film it will just as well produce a picture, no need to be picky. Just trust in the process and make pictures that make you happy.
