I remember we did something very similar to this in the very first boxfit session at the gym. We gave them pegs to stick on their tops, and the idea was to grab your opponent's peg (mmmmatron!), whilst protecting your own. Anyway, that was the first and last "peg game" session, after we got an eyeful of side-boob, numerous times.
well on the plus side shoulder tip is a lot faster and more continuous because you dont have to keep putting the peg back on your shoulder but the downside is a lot less side boob.