I may be wrong, but I think it helps contrast by proportionally building stain. So I would think more stain on the parts of the negative that are exposed more would make those mid to high zone levels move up a bit. I tried this procedure last night and it worked really well. The developer I used was pyrocat HD. While it did help my negatives a lot, it still wasn't enough, seeing as how they were greatly underdeveloped to begin with. Next I plan to run the roll through In-5 to increase the silver density. Hopefully this will solve my problems.