13x13 at IYT rarely fills and 15x15 pro version is even rarer...i've personally never seen it happen....so 15x15 would be a good size...20x20 is more of a "Go" size.
(hide) If you want to play a game with an opponent of a similar level, you can define a required BKR range for a new game invitation. Then nobody with a BKR outside this range will be able to see/accept it. (Katechka) (show all tips)