I've heard some about this too - a friend of mine went to London and studied for him for a year perhaps. He told me that Feuchwanger made stretching excercises which actually improved his stretch quite a lot (he reaches an 11th with no trouble now), but I don't know what sort of excercises that was. I could ask him... But I do know that he did a sort of "finger-control" excercise which was something like this: put your hand on the piano, completely relaxed, and let the other hand "tap" one of the fingers, just once, so that you get a sort of sforzando, or forte. Then, try to focus completely on just that finger and try to make it sound just as when you were tapping with the other hand - BUT without moving the rest of the hand or fingers, and staying competely relaxed. It's alright to focus on doing it for a while, but the motion of the finger should be as fast as possible. It's hard to explain here, would be easier to show you, but I hope you get the idea... I haven't done that excercise too much myself, but I know that Glenn Gould talked about this too, incorporating this excercise to his practicing.