I believe the best way to find the perfect left-hand grip is to do the following:
Stand up straigt with the club in your top hand. extend the club out in front of you so your left arm(for a righty) is pointing diagonally to the ground. If you are holding it correctly, you should be able to remove your pinky, ring, and even your middle finger off the bottom of the grip while still holding the club out in front of you. You should be able to hold the club with your palm and index finger supporting the club on the top and bottom of the grip, repectively.
Give it a shot!
If you wish to have a visual, send me a personal message and i can take a picture and post an image for you.
MyGolfster.com