As a former ref, I was told (and believe) that the players determine the level of play and amount of contact. I tried to to maintain the flow of the game and ensure the safety of the players. At the pregame instruction, I told the players and my assistants what I would and more importantly would not allow. Example, two men standing together with arms by sides going up for a header SOME contact allowed; one guy taking a five yard run then coming over the top of a stationary man and "accidently" hitting head with forearm = red card.
Two quick comments: 1. With a two man system, you will NEVER be in position. The players are too fast and can change the position of the ball much faster than you can run. 2. Don't forget that the refs have "played" every minute of the game and probably just did the JV game before. Even people in great condition will slow down towards the end of the game.
