I don't have a set system either, but when they get rowdy and knocking the other eggs around, if no one, or at least some aren't zipped 3/4 of the way, I yank the chicks out quickly. I think I have more losses here from the soccer players than I do, due to a humidity drop. My bator gets the humidity and temp back pretty quickly.
That's kind of what I've been thinking....I just can't tell in the back all the way what the progress on the eggs there are because of how much the chicks are wriggling around and huddling around the unhatched eggs, so I'm just not sure. I'll try to hold off for a while longer at least, but I'm thinking they're gonna have to come out soon. They really are scramblers!