Please don't do a rule unless there is an actual problem. God knows we have enough of them made for that reason. Frankly I don't see a problem with more than one team upstream. I will have to say that in the 11 or so years diving that system I have only been there with a second team once. If you guys are really worried about multiple lines then just run the gold line out. It's not like your going to have open water divers using the site, you do restrict the keys.