When I choke down on the grip - let's say a full inch between the rear pad of my top hand and the end cap - I hit the ball more flush and straight. This does cause me to stand a hair closer to ball with a more upright swing. When I get out on the end of the grip, I seem to hit pulls more often than not.
I realize this is subjective but how far is the back edge of your upper hand "suppose to be" from the end cap? Thanks.