Aggie, I don't know anything about this other than the discussion over at Michael and Paula's site. I made some 4x5 negatives this weekend, one side shot with shadows at Zone II, the other of the identical scene with shadows at Zone IV, as Jim suggests. Perhaps traffic will allow me to get home in time tonight, and with enough energy left, to make some prints. Then I may have an opinion. Or more questions.
Doug, the discussion is not about resolution, but about getting "the glow" from the PL100/Azo combination. Jim's observation is that getting "the glow" with Azo requires a more dense negative - not contrasty, but dense.
Doug loaned me his BTZS book a month or so ago, and I read it with great interest. It gets far more intricate than I feel like getting with my personal photography right now, but I noticed one thing that struck me. I know many people get very good results using that method, so this is just observation, not criticism. In the book, everything moves along with a lot of precision until it gets to the topic of metering. The book recommends incident light metering in the sun, then metering in your own shadow to determine SBR of a distant scene - not metering the actual values of the scene itself (as I would do with my spotmeter.)
That tells me personal metering habits may be far more important than we (I ?) have given them credit for.
Again, I recommend anyone using Azo to read the thread at Michael and Paula's site - there's a great deal to at least think about there.