I shoot Ilford Pan F Plus 50 ISO, 120 film, but I have rated it at 80 ISO, and I develope with HC-110 Dil. B (2:14) in a steel tank on a reel. The manufacturer says to give 4 minutes development, but I find that if I develop for 5 minutes that it raises the density of the negative and boosts the contrast, there is a very noticeable difference between 4 and 5 minutes, could this be considered a one stop increase in such a quick amount of time. I do not find the negative densities objectional. I think they would print well with a diffusion enlarger. Any comments, or suggestions?