When he related Jack Nicklaus' compliment, he was uncocking and rolling his hands - very quickly.
To him , handspeed was the sequenced release of the swinger - uncock and roll.
That said, I agree with you on the role of the upper arm but I still do not completely understand its role in producing clubheadspeed thus have not began isolating them in training yet. I will be most keen to share once I reach a conclusion.
One thing that stuck in my mind about Sean was the size of his Extensor carpi radialis longus and his Pronator teres. They resembled sausages.
There is a rhythm to centrifugal force- trying to make it go faster really isn't a viable option. Training "just" the muscles below the elbow- doesn't make any sense at all. Finally, could you identify the research that says the body only provides 10% and also that the transferring of the weight only 2% because both of those "facts" are much like training the muscles just below the elbow- they don't take into account the entire context of the movement. Anotherwords- if I didn't transfer my weight and hit off my back foot- I really wouldn't lose any power?