To answer exactly where the lead thumb position was not the club shaft, you can see here some important factors.

1. The thumb is medium length, and the thumb pad is securely at the club however the thumb is not entirely on the grip.
2. There is a gap between the thumb and the hand – between the thumb and knuckle of the index finger.
3. The thumb is just to the right (right handed player) of the center of the shaft.

Here is another picture of how the lead thumb was placed. This photo is taken from our Product Training Manual.