I'm wondering about the developer as well. I use D76 for Tri-X, and I have used it for HP5 as well, but Acufine gave me a look w/ the HP5 that I preferred. One thing I would suggest (and I wish to goodness I would follow this myself) is to make only ONE change and see how things go. Usually, the differences in ISO that you're talking about are pretty small when shooting HP5. Developer choice, developer freshness, agitation procedures, the light that you took the photos in, your metering technique, etc can all influence what your neg looks like.
I also concur that even though the negs may look different, you may not see much difference on the prints if you use your graded papers/filters to get a print that you like. Since the neg is the next to last stop in the process, I would make some prints and see what's up.
Last edited by momus; 10-15-2013 at 12:53 PM. Click to view previous post history.