We tried this concept many years ago and discontinued it because to many were getting injured. It's one thing to fight multiple opponents, when you can remove them from the situation. It's entirely another when they can constantly come at you and all you do is attempt to keep them off for a short time. It's an exercise in futility, but it can teach you, to an extent, how to zone and use one attacker as a shield, but that's still on a very limited basis. Now I will grant you, it depends on the allowed aggressiveness of the participants, but it only takes one to up the intended level and things can and do get spicy real quick, with the inevitable injury following.