Perhaps Sandy or Clay can weigh in on this subject. It has been my experience that any of the pyro formulations that have a tendency to provide a green stain on a negative (PMK, and ABC when the bisulfite has any age) will have the tendency to decrease contrast on variable contrast materials. That much many people have already covered before.
Has any research been done on the apparent density effects of the brown stain on VC materials. It would appear to me that the brown would have a componant of red (albeit small) that would have the effect of some contrast increase on VC materials.
I wonder what would happen if a pyrocat neg was read through the red channel on the densitometer? Has anyone done this?