I just got to through in my $.02. I have a Jobo tank for 4x5 and motor rollers. I do use the motor for high energy developers but no longer for staining developers. PMK is a fairly weak deveolper and (thank goodness) pretty cheap. I mix up 1.25 liters of chemical to develop 6 sheets at a time (or less). I find that hand agitation with PMK offers noticably better accutance than using the rollers. I think the constant motion of the developer interferes with some ridge deveopment reducing some accutance. When hand processing, there I invert and swirl for 5 seconds every 25 seconds and noticed the improvement. I could never get good results with PMK on rollers when trying to develop more than 4 sheets with 500cc. The extra fluid prevents developer exhaustion.
Frank