Disagree, Mike. I just drove three golf balls across the highway into the woods, and my grip puts the palms roughly in the same plane. Ditto for a baseball bat. You honestly grip a golf club and a baseball bat with the palms at right angles to each other? Shotguns are totally different anyway. The fore-end hand does the leading and guiding when swinging a gun. It should provide the control of the barrels. The hands are nearly two feet apart on a gun, together on a club or bat.
I also mounted my Perazzi several times, just as I do when premounting before calling for the bird. I have a habit of wrapping my left thumb over the rib (I am right-handed, and have medium sized hands) when mounting the gun. This automatically puts my left palm roughly vertical, not perfectly so, because a little of my palm is under the left bottom edge of the fore-end. Then, when I'm mounted I lay the thumb alongside the top edge of the fore-end with my fore-finger pointed right down the axis of the barrels. This leaves three fingers to wrap under the fore-end and curl slightly up the right side. It is a very secure grip for me, and has been working quite well for some time now. The left palm is not perfectly vertical, but MUCH more so than when I grip my S x Ss.
I cannot believe you guys who actually try the experiment I suggested cannot tell the difference. To me it is like night and day, and trust me, I am NOT one who is easily swayed by the power of suggestion. It just feels much more natural and right to me.
I shoot my S x Ss pretty well, for an old fart, and compete with them as often as I can. Use them for birds a lot, too. But, the swing just does not feel as natural, much as I love them. Come on fellas, try it with an open mind and try not to be defensive about these guns we all love so much.
SRH