If you're like me, you get annoyed at how easily the dummies roll out of the fighting zone, especially when the ninja pushes the dummies out simply by walking at them. Then when you bring the dummy back in, it lands funny and rolls out or knocks your ninja over (wasting so much time) or manages to do both. Hence, I suggest using two dummies at the same time. This way you can bring one dummy back into the zone while the ninja is messing about with the other one. Two for the price of one, people. Quicker and less annoying.