And not to hi-jack, but I think the league admin's should be able to choose the number of races, and the order of the races, or leave it to be randomized.
P.S. Jack, if you need someone to make the other 4 tracks, I can do it. ;)
Not sure what difference it would make between 17 or 21 races, it is long enough a season as it is, 1 week and a half for some leagues a season, for others it would be longer, but really another 4 races isn't going to change much anyway.