One problem with doing a sunday afternoon is if the tourney is at a church it needs to be cleaned up or set back up saturday night for the church. If it isn't cleaned and set back up because everyone is planning on playing more on sunday that could pose a problem. Also, although I've never been to a Nats I'm going to assume that Sunday is a travel day many times and if there are more games or categories that travel day becomes monday which means another day off taken which makes Wednesday just as viable an option. The one thing about a 4th day is it would be optional so not everyone has to make it or stay for it if they couldn't or didn't want to.