When a man stands freely, the natural orientation of the direction of palms and elbows are as follows:
The direction of both elbow sockets is in line with the direction of palms. The clavicle bones are in a perfect neutral position. It remains the same when we bend as in the address over the ball:
When we move both hands in order to blend them together they are still at a 90* angle towards each other, therefore, one of two hands is on top of the other being simultaneously perpendicular to it; on the pic, the RH is on top because it is like this in reality on a grip:
The 90* angle between both hands ensures the maximal possible effectiveness of the wrist movement in the swing - the lead wrist cocks/uncocks (radial/ulnar deviation) while the rear wrist hinges/unhinges (dorsi/palmar flexion), and the orientations of those motions are exactly perpendicular to each other:
In order to achieve it, the lead hand grip should be as strong as possible (with the so-called short thumb for control)...:
...while the rear one should be as weak as possible...:
...without and lack of comfort. Some people can achieve a bigger angle between both Vs, some a smaller one. What is worth remembering is the bigger (or better said the closer to 90*) the angle between both Vs is the closer we are to the maximally efficient grip. However, there are some anatomical limits (different for different people) that are great checking points. First, there should not be any gap between the ring finger and the grip. Such a gap can be created when the RH grip is too weak. Secondly, the RH pinky finger should be able to hook around the LH index finger and the strength of this hook must be big enough to ensure a proper tieing of both hands.
The Vardon overlapping grip is the best for two reasons: 1) it lets all the fingers (except RH pinky only) lie and exert pressure on the grip; 2) RH pinky finger can easily wrap around the mid joint of the LH index finger, because, as all fingers, it has three parts and two joints. It should look either Mr.Hogan presented in '5 Lessons' or, in an exaggerated to the maximum version, like this:
Please note that such a method of hooking the pinky finger is much more stable than a conventional method of putting the RH pinky finger in the slot between mid and index fingers of the lead hand. The more, with a strongish position of the LH the LH index finger becomes in sort of a trigger finger position and the mid joint is being raised, creating a great base for the pinky's wrapping around action.
Finally, the weak RH position on the grip forces automatically the RH index finger to be in a trigger position, that is really important in sensing the lag as the most important pressure point on the grip.Moreover, the weak RH position creates the optimal condition for presetting the rear forearm turn at address (that has a lot of importance in both the upswing as well as the downswing). The preset should be visualized more or less like the combination of the weak RH and keeping the elbow socket up from the beginning till entering the impact zone (what Mr.Hogan recommended to Mr.Venturi):
Please take into account that the above mentioned photos are an exaggeration presented so that the whole concept is clearer.
Lastly, the desirable takeaway effect of the Bio-K Grip, namely, the rear elbow socket up during the takeaway - first, the BGST author statically...:
...and then the Golf Master dynamically:
