[strav]

The left thumb position, I was playing around with a club and I noticed I could slide my left thumb further up the shaft and this would allow for more left wrist cock. What is the preferred location for the thumb? Short or long?

Thanks!

John Daly uses the 'short' thumb and agrees with your observation.
In 'The Killer Swing' he says "I’d like to add here that when I place my left thumb on the shaft, I don’t extend it as far down as possible but rather inch the thumb up slightly in what is called the ‘short’ thumb position. This minor adjustment feels secure to me and also, I believe, allows me to make a fuller wrist cock at the top of my backswing.
Of course, as you assume this left-hand position, you should be aligning the leading edge of your clubface square to the target."

Doesn't seem to restrict his swing too much.