[Howard Klepper]

I didn't read beyond the first page, so this may have been said already:

Larry's method of placing his thumb lower on the neck than where he is barring and using it as a fulcrum is wrong according to classical technique, and would be strongly discouraged by most classically trained teachers. All the ones I have seen say to place the thumb just above the barre--between the barre and the next finger. And they say not to try to either use the thumb as a fulcrum or to squeeze hard with it, but to pull against the neck with the arm while securing the body of the guitar with the right fore arm just beyond the right elbow. This way the left arm, especially the bicep, does the work rather than the thumb.

I have no doubt that Larry's method has been successful for him, but I think it ought not to be presented as The Right Way to make a barre chord. It is an unconventional way that may work for some.