http://www.metacafe.com/watch/4668814/1997_wch_ms_final_peter_rasmussen_vs_sun_jun/ @23:44 Sun Jun did the smash with the shuttle behind his body. Could somebody analyze how he swung his racket to generate the power and the grip that would be fit for this situation? Thanks in advance!
I agree with kenzo. I might imagine that if the shuttle went behind him, he could make a small adjustment, turning the grip ever so slightly towards a thumb grip - not using it that way obviously, but turning it ever so slightly in his hand to make contact from behind on the forehand side easier. However, perfectly possible without this adjustment too. He makes it look easy because he uses the most natural grip for hitting in the direction he wants to hit from where he takes it. p.s. thats a truly great match. Look at Peter Rasmussens footwork. It is incredible.
I'd say there's more to the shot than just the forehand turn. If you were to understand where the best location to hit a smash is from in front of the body and moving forward you can get a better understanding of this shot. In this case he is moving backwards and away so he isn't turning his weight into the shot so it takes an element away from the conventional smash. But he does take it in front of him and he does this by leaning backwards so that the bird is in front of his head. That way he can still get the rotation over and on top of the bird.