I need a film for indoors without the use of flash. I just started experimenting with Fuji Neopan 1600 indoors with incandescent lighting as well as natural light during bright daylight. I used the MDC and developed in Xtol 1:1. 7.5 minutes when exposed at 1600, 6.75 minutes when exposed at 800 and extrapolated to 6.5 minutes when exposed at 640. I found that at 1600 and 800, there was underexposure of the shadows. At 640, the shadows are about where I want them but there were overblown highlights; just too much contrast. I want to cut my development time down to 5.5 minutes, just under 20% less development. How do I know when I've gone too far? Would the prints just be more muddy or would there be some more catastrophic change?