Hairy - the usual reason the R22 blades hit the tail boom is due to negative (or just a sufficient reduction in positive) G.
A teetering head helicopter hangs underneath its rotor and tilting the rotor drags the fuselage along with it, be it in pitch or roll.
When the aircraft is subjected to negative (or reduced positive) G, the effective weight of the fuselage reduces (to zero at zero G) and the rotors can move wherever they like but the fuselage won't follow as the teetering head cannot exert any leverage on the fuselage (unlike on an articulated or semi-rigid rotor).
So the only thing producing any thrust that can affect the fuselage is the tail rotor. In a low G situation the pilot is more likely to make large cyclic control inputs (trying to control the attitude) which will have negligible effect until normal G is restored and this results in mast bumping or, in extremis blade contact with the tail boom.
And people wonder why I don't like Robinsons.