Less than 11 players and guys get too many minutes. More than 12 players and some guys will not get enough minutes to be useful. If you are going to do 1-position training (Inside Defense - Center for example) try to get each of the three trainees 48 minutes a week to get full training. More than 48 gets no extra benefits and less than 48 minutes will cause fairly big drop offs in training. If you set up the starter, back up and reserve as the same player and set the team to let them play with fouls you have the best shot at getting 48 minutes for a player in a game.