Lu,
I tried to prove your theory, not disprove it, for both my own reasons and to do credit to your logic. It seemed to be the right way to do it.
I didn't find any evidence to support it and in a quasi-scientific way I have to go with what the evidence suggests, ie. there is nothing inherently wrong with the R22 or 44 rotor systems.
Indeed, Mast Bumping has been painfully demonstrated not to be isolated to one type only, but occurring in ALL underslung and /or teetering rotor equipped helicopters.
The R22 and 44 definately suffer from poor pilot awareness of the risks low or negative 'G' (Still!) and far more low time Pilots fly them than any other helicopter. That may well be the cause of more accidents of this type, for this type.
In any event, I refer all that may not have seen my recent thread on 'Mast Bumping and the danger of low or negative G' to it, as it is clear that pilots with less than sufficient knowledege of the risk are still out there.
SPS