[BC85]

I would suggest setting the right hand (assuming you are right handed) on the putter so your forearm is in line with the shaft and take a few practice putts just with your right hand with the number one and three pressure points directly behind the shaft. Then add the left hand to the shaft with the shaft running up through the lifeline of the left hand. Both thumbs should rest on the top of the grip. It may help to initially run both forefingers down the length of the shaft.

Thanks for the reply, Jerry. I can get the shaft running along the lifeline of both hands when they are gripped in a non-overlapping manner or individually. However, as soon as the right hand overlaps the left hand (i.e. using the reverse overlap grip), the shaft shifts to below the right forearm but remains inline with the left forearm.