Concerning Ilford Delta 3200 and FB+Fog...
I recently "standardized" my equipment (camera, film, meter, developer, enlarger, etc) for Ilford Delta 400 Pro and rated it at ISO 250. The rating is based on the minimum time needed to achieve a maximum black print through an unexposed portion of the negative and the practical ISO needed to still get a Zone I exposure. After the success I had with Delta 400 and "standardizing" for the Zone System, I thought I would do the same for Delta 3200 so I could have a low-light film in my arsenal. Unfortunately, even a Zone V exposure shot at box speed doesn't yield a Zone I print at dmax print times! I'm attributing this to the high "density" of FB+Fog since the exposure to achieve a max black print is more than 2.5 times that needed for Delta 400.
I still like Delta 3200 for low-light photography but I'm disappointed I couldn't "standardize" for the Zone System with it. I really like the pre-visualization I can achieve with the "standardized" Delta 400...it makes printing so much easier and predictable.