Glad it was a model not the real thing. Of course a real helicopter could not do it. A lot of the spins are due to torque generated by the main rotor head which is normally counteracted by the tail rotor.
Although this click here= is a 3D generated view of a Seaking doing a wingover the actual manouevre is not that different. In the mid 70's I was the crew in an air display. We did about 20 of these wing overs. I can remember just about each one. We used to do it as a synchronised pair low-level and gave up when the second nearly hit the ground.