Arriving late at the party, permit me to toss a random thought into the mix:
I've perused this entire thread, and I saw several mentions of the Weaver "stance" (and "modified Weaver"), but I don't believe anyone actually mention good old isosceles (sp?). I think it was Jeff White who said his combat stance is almost frontal, but then he intimated that he nonetheless consideres it to be "Weaver."
Correct me if I'm wrong, but doesn't true Weaver involve not only putting your upper body at an angle to the target, but also sharply bending the support arm while keeping the strong arm extended almost straight, and -- most importantly -- pushing the gun forward with the strong hand while pulling back with the support hand. What old Charles Atlas usd to call "dynamic tension."
And, given that dynamic tension is part and parcel of a true Weaver technique, I can't accept that this won't degrade over time, or that it won't simply disappear under stress. Once I departed from the one-handed duelist stance I shot in competition when in the Army, I gravitated to isosceles. But I guess it could be called "modified" isosceles, because I do advance my left foot about 6 to 8 inches ahead of the right. What I do NOT do, though, is attempt the Weaver-esque dynamic tension, push-pull thing.
Out of curiosity, a few months back I spent some time at the range and made a conscious effort to shoot from a true Weaver stance, including the dynamic tension part. I found two things. Even though visually I was aiming the gun the same, my point of impact dropped several inches at 10 yards using the Weaver technique. I reckon that dynamic tension is more effective at resisting muzzle flip, and muzzle flip does affect point of impact. That, by itself, isn't a big deal -- as long as you always shoot that way so your point of aim is (or your sights are) adjusted accordingly.
The other thing I found shooting Weaver was that I tired much more rapidly. I usually shoot .45 ACP, standard power loads out of a 1911. In my normal shooting position/stance/technique, I'm not especially tired after several hundred rounds. Using the Weaver, my arms were shaking after about 50 rounds. Any semblance of accuracy went down the tubes from there on.
I went back to what I know and what has worked well for me for many years. Can't teach an old dog new tricks, I guess.
The summary point to this novelette, I guess, is simply that there's more to what separates Weaver from Isosceles than the position of the feet or the angle of the arms. If you're talking about true Weaver, you're also talking about dynamic tension. And that, to me, seems UNnatural. That which is unnatural is likely to go away under extreme stress.