OB Left
You wrote-: "Have you ever broken 90?"
That statement is really an ad hominem style comment, that doesn't make your argument about TGM issues more-or-less legitimate.
Stick to arguing for your viewpoint regarding TGM/biomechanical issues. You are entitled to your viewpoint, but you are not entitled to
arbitrarily assume that your opinions are more "right" than mine.
You wrote-: "You seem to keep implying that secondary axis tilt assumes the head to move back of center."
There are two ways to acquire secondary axis tilt. Your way (and mine) is to keep the head central and shift the pelvis left-laterally, which then shifts the lower lumbar spine left-laterally thereby creating secondary axis tilt. However, there is only a finite amount of space between the center of the stance and the left foot, and the body with its
desired degree of secondary axis tilt has to fit within that space. Tiger Woods and Mike Austin and Jamie Sadlowski apparently need a greater amount of secondary axis tilt, and there is no room between the center of their stance and the left foot to accomodate that
desired degree of secondary axis tilt. They therefore choose to have the stationary head further back - behind the center of their stance.
I believe that adopting a large degree of secondary axis tilt may be advantageous for driving the ball a long distance, but I think that it is not optimum for accuracy/control. That's why most tour professionals keep much more centered, and adopt far less secondary axis tilt, when hitting their iron approach shots.
I am incapable of adopting large degrees of secondary axis tilt because I lack the spinal/torso flexibility, so I do not have the ability to make these personal choices.
Here is a nice video clip - presumably by VJ Trolio
He shows four variations of pelvic pivot action movements. He obviously favors the last one.
I think that many tour PGA golfers prefer the first one - the conventional pivot action where one loads over the right leg and where the head is positioned slightly behind the center of the stance. Hogan used that conventional pivot action for most of his career. Are you arguing that it's a totally unacceptable choice - from a personal, or TGM, perspective?
Jeff.