While I expect that they are showing off, I can make up some excuses for such acrobatic behavior. I think they are goofing off because the situation the crew has placed himself in, is very risky in the good verses potential harm ratio.
Now, if for some strange reason the helmsman could not get himself farther toward the lee side, then lee trapezing by the crew could have been needed to get the windward hull out of the water. Otherwise, separating the two sailors' body masses should be counter productive. I can think of one exception.
Perhaps the skipper's ability to quickly move to windward, if needed, can justify his need to stay on the high side of the boom. This may explain his situation. Any farther forward and he'd have trouble operating the tiller extension. Any farther to lee, while so far forward would present the same steering challenge. Also, his forward placement is beneficial.
GARY
Mr 6.0 [color:"blue"]WHISK [/color]