Testing with 35mm film is a good idea: we can save on materials and more easily test extreme enlargements.
If we want a subject in the shadows to end up on Zone IV (as with the barn image above) then yes, we can place it there and let the high values fall where they may. This is one of the attractions of Divided Pyrocat: expose for the shadows, period.
That being said, a white horse in the shade ? a black cat in the shade ? Should they both be placed on Zone IV ? Not all "shadows" are the same.
As with all other film testing I have done, I found that using the published formula and developing times, Divided Pyrocat gives ~1/2 box speed: 50 for TMX and FP4+, 200 for TMY and HP5+, etc. We can split hairs and use 64 and 250, but the differences amount to a fraction of an f/stop, often beyond our ability to precisely meter a scene.
I should point out that I stopped using Divided Pyrocat because I couldn't always avoid uneven development. At that time, I developed sheet film in trays and did not want to give up development by inspection and adopt rotary processing. Since you use a JOBO, you may not have any problems.
Please share what you discover. I am happy to be proven wrong
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