Instead of having to opt out of the derby why not make it you have to opt in to play the derby? Reason is we have several players in our group who haven't played in months and the leader doesn't want to boot them. We were talking and I came up with this idea, so thought I'd suggest it. This way if everybody starts out as not playing if you want to play the weekly derby you have to opt in and when you are going to be away you opt back out again.

