On the overlaps, they can occur anywhere, not just at the (2 length) zone, and it's also which boats actions caused the overlap. If the port boat in the example had it outside the zone, the stdb's are going to have to give some room. But if port tries surging in there too late, inside the zone, well that's what the rules are trying to prevent. But if I was on stbd, I sure wouldn't like it if a singlehander on port took me down with him a couple of boat lengths, instead of him prudently taking down the kite sooner, accepting he can't maintain the overlap.. esp. if the boats I was beating to the mark are now happily zipping through the gap that's been created.