rotational or translational movement with the skids near any obstacle is a high-risk exercise, may look exciting but it is not far away from an RUD, and that puts spectators at risk. DK did that over surveyed areas, where he was aware of the surface, and away from giving the crowd a face full of blades 'n bits.
The people at this show looked plenty close enough to get a face full of debris if he had rolled it:
How far do MRB bits fly?
The rest of your post was quite extensive, thank you, but already evident to me with two exceptions:
I've flown an R22 in a test at 56kts to the right and 55kts to the left, and yes, the helicopter can do it...It was also not done with the off the shelf R22, which hit the limit in flight to the right much earlier.
That's extraordinary. I would not have thought even a not-off-the-shelf R22 could do that. I am curious about the rest of this story. What were the modifications?
Final comment, note when you come out of the right-hand high-speed flight, that suddenly unloading the TR which swings the nose into the direction of flight will most times give a prompt overspeed of the engine (and MR) the governor is good, but not that good.
That is something I had not considered. In your professional opinion, from the video evidence, do you feel that there were such over-speed events during the flight in question?