I don't think this is an accident waiting to happen. Infact the pilot appeared very experienced and skillful to me. He minimised the take off and landing path over the few people on the beach, aparently he had been doing it all day and no problems with the machine or his skill. AH on the pi55, so what?. Low RRPM going off occasionally, so what? perhaps the clutch light flashed a few times too. SO WHAT? Negative G push over? now if that was true I would agree but I did not see any, looked all positive G to me.
Why is it you are all quick to judge and condem others who are harmlessly enjoying them selves. If you don't want to show boat, then don't. But please, if others do it and do it safely, as was the case here, then so what?