To establish a developing process for your Pan-X, now some 35 years old or more, why not start with Kodak's original recommendation: D76, 1:1, 7 minutes at 68 degrees (small tank.normal agitation)? I would shoot a couple of test sequences on one roll from the 100 foot roll. (The separate cartridges may have aged under different circumstances.) I would test ISO 10, 20 and 32. (It didn't get faster with age.)