Setting up challenge games really won't help with the problem of players mistakenly signing up for the wrong side though. It would only limit who could sign up for a given game and that is not the issue here. Furthermore, it requires both teams to have a specific list of players for a given game. I think this would create extra work for squadron leaders. It would be necessary to contact the players and get a reply back to verify that they are available and interested in that game. I like the password method, even if the sign-up period is only 48 hours, because I can notify everyone in my squadron with a single e-mail that there is a game available along with the password so that any of them that are interested in that game can jump in.