You probably haven't been following the pivot center thread - in terms of my personal views. I don't believe in the idea of a pivot center or a pivot axis.
I simply believe that one needs a small degree of rightwards spinal tilt at address and an appropriate amount of seconday axis tilt at impact.
For short-mid irons, I like Yoda's approach where one places one head in the center at address and acquires a small degree of rightwards spinal tilt by shifting the pelvis slightly left-laterally. That should produce a small degree of positive O factor at address -which RB demonstrates in his video. Because one is hitting a short iron, one doesn't need much secondary axis tilt at impact. HK stated that one should place one's head in the position it will need to be in at impact. Because there will be little need for much secondary axis tilt when hitting a short iron, a centralised head position works very well and complies with HK's recommendation.
For a driver, I think that the head should be positioned back of the center of the stance - roughly midway between the center of the stance and the right foot - because one anticipates a much greater amount of secondary axis tilt at impact. One still shifts the pelvis left-laterally a small amount at address, and that produces a small amount of positive O factor. During the downswing, the degree of secondary axis tilt is going to increase because of a more significant amount of left-lateral pelvic shift onto a braced/straightening left leg. That left-lateral pelvic shift onto a straight left leg produces a definite positive O factor in a driver swing (more than is seen with a short iron where there is virtually no left-lateral pelvis shift in the downswing).
In that sense, I agree with RB re:head position. However, he makes a fetish of the degree of positive O factor and claims that a greater degree of positive O factor at impact will increase clubhead speed. I disagree. I think that the amount of secondary axis tilt required (amount of left-lateral pelvic shift required) depends on the golfer. Jamie Sadlowski and Tiger Woods and Mike Austin have a large amount of secondary axis tilt at impact. However, many other excellent golfers have a lesser amount, and still hit the ball a long way.
Out of interest - here is a series of images of Mike Austin.
Note that his head is well behind the center of his stance at the end-backswing position. Note the significant amount of secondary axis tilt he has at impact and note the significant amount of upwards tilt of the left pelvis at impact (large positive O factor).
Here is Jamie Sadlowski
Note his head position - behind the center of his stance. Note his significant amount of secondary axis tilt and his positive O factor.
Threaded Mode
