You might consider that control comes from the support hand. In a variety of shooting disciplines and with mechanically different guns. When shooting a pistol you want a firm grip with the firing hand but a hard grip with the support hand. When shooting quickly at short range with an AR, you want more grip and pulling back into your shoulder with the support hand and again just a firm grip with the firing hand. These are for slightly different reasons, increase speed of the trigger finger, but it demonstrates that control doesn't come from the firing hand grip. When you're shooting a long gun, your firing hand grip is the 3rd and sometimes 4th point of contact. Your cheek, shoulder, and support hand(wether on the rear gripping a bag or on the foreend applying pressure on a bag on a barricade) are supporting the gun in it's NPOA. The firing hand should not support the gun. And on top of all that the ultimate goal isn't just to lay down and shoot tiny groups at 100, it's to shoot the same zero out of multiple positions. So are you going to maintain the same pressures with the firing hand grip off a barricade and a tripod, or off a bag? Probably not.I agree that the shooting hand can play a big roll. I've decided that I like having complete control of the gun with the thumb wrapped around the grip. Three fingers pulling back into the grip/shoulder can pretty quickly turn into slipping and dangling on a grip with any kind of angle. But I'd still prefer to get that tension from my firing hand than my bipod.
Thanks for the insightful comment. I'd like to spend some time on a large frame to iron these things out.
One parting shot. Here's what I'm shooting using the technique I described above with a 20" WOA. Might be worth at least trying.