No, it's not possible to get each player 48 minutes per game. If you just have five players play, all of them will get 43 minutes. Rather, set your starters to be different players than your reserves and backups. So, your starters will get exactly 36 minutes, your backups will get 10 minutes, and the reserves 2 minutes. A player can be backup and reserve, and gets 12 minutes for this. Focusing on two-Position training with five trainees looks like the way to go in such a situation.