No mast bumping-BUT!
Given that a fully articulated rotor cannot experience mast bumping under zero/negative G, there is another matter which may "curtail the curious" in the exercise of these manoeuvres.
And that is the consequence of placing the T/R thrust line above the main rotor.
Given that, in order to demonstrate the preamble to catastrophic mast bumping with a teetering rotor it is necessary to have "considerable" power on to cause the heli to roll right, when teaching the correct recovery technique from a low G situation. (I speak of the R22)
The technique of course, being to move the cyclic aft to load up the rotor.
I have always presumed that the right roll so induced was brought about by the T/R thrust being above the M/R. Am I right in so thinking?
If so, it seems as though one could induce inadvertant barrel rolls with a fully articulated rotor, at the very least!
thekite