So, after all this, now I'm wondering what is "release"?
I am starting to get a tiny bit of feel for a "double pendulum effect". Is the place where it seems to move the fastest the "release"?
Is the double pendulum the correct way of thinking about a swing?
What is it? And what do you feel when you are "releasing"?
Does it even make any sense to think of it this way?
well, they say that the golf swing is somewhat similar except it's completely upsidedown, to a medieval siege engine called trebuchet.
Trebuchet was the terror of medieval times in warfare, used rather successfully even by the Spanish conquistadors against the aztecs in siege of Tenochtitlan.
Trebuchet wooden arm would equate to golfer's arms
trebuchet sling rope which attaches the ammunition into the wooden arm equates to golf club.
here's a picture analysis of bobby jones's swing, I don't know if it's accurate though, with the old technology of the 1940s used for motion-imaging.
More calculations about golf swing here http://www.real-world-physics-problems.com/physics-of-a-golf-swing.html