It's awfully hard to put down any hard and fast rules, because as soon as you do, you'll find a combination of person and undergarment and suit that just won't fit. Bob Sherwood spent an entire MORNING convinced he could trim me out in LP72s, and at the end of it, he a) acknowledged that I have to carry as much weight as I do, and b) concluded that no combination of weights was going to trim out those tanks and me. Ankle weights would have done it, but I don't want to wear them, so I leave the 72s to Peter, who can't trim them out either but doesn't care. 
