Three hands is plenty of people to work a pair , especially when empty, no crew required, send one down with motor and leave two on the butty, just remember to tow on the longer pounds at atherstone. I just love the mentality of trust boats that seem to think they need dozens of people to work a pair through locks. In my opinion as daniel says any more than four your tripping over each other. In any case its efficency, not the amount of crew or running to set the locks its being in the right place at the right time with the mininum amount of effort, rant over for now