I cannot trust these results yet. There was to little difference on the four stop series, i could not believe it, no film is that forgiving. I used a studio flash and took shots from f5.6 to f16 where f8 was EI 400 confirmed on my digital camera. Today i put the old Chinon 28mm lens i used on my digital camera and yes i have a bit sticky aperture blades. It works OK with flash up to f8 but over that the blades are not fast enough to stop down fully until the flash comes on, there are probably a little oil on them and the camera was a bit cold from being in my garage at 8C. That explain the very small diff. i saw on the two darkest shots. But of course this only apply to the shots with that lens using flash, without flash the aperture blades are fast enough.
All other shots i made was with another lens. So far.. 1:25 Rodinal and 8 min seem to be quite spot on. 1:50 and 12 min came out a bit darker, less than ½ stop, with less contrast. More testing is needed, 12 min for 1:50 was not enough for my taste, or i may just settle on using 1:25 for Hp5+ at box speed. The diff. in grain was negligible while i liked the tonality of 1:25 better.