Horses for courses
Brian,
As it seems to me that there isn't just one pivot for all shots and the selected pivot has to match up with the club, your objectives and the shot at hand I'm at a bit of loss why you would compare Stewart's swing, with what looks like a 6 or 7 iron, maximum a 5 iron, with a Sam Snead pivot with a driver or fairway wood. Why would you want to go that far right with an iron, especially with Stewart's ball position? His chances of getting rid of his "high floaty fades" wouldn't, on the face of it, seem to improve.
If you compare Snead's swings with different clubs in his classic "How to play Golf" book you can clearly see how the pivot changes with the club. Page 73, bottom right hand corner, top of the swing with a short iron, he's left of a tripod centre, it seems to me. p59 Top of the backswing with his Mashie, angle not very good but he doesn't look very far right, take a look at the creases in the top of sweater as well, cervical spine to the left of his thoracic spine, thank you to David Orr for that insight. Long iron further to the right, but not much more. With his driver he's further to the right again, with the base of the neck just about in the middle of his feet.
Hogan Power Golf, the same, short iron, p116, base of the neck slightly nearer left foot than right, longer iron, p142 base of neck fractionally left of centre(?), driver swing p63 base of neck right in the middle of his feet.
Gary Player, now I know why he won 9 Majors, p82 Golf Power in Motion, 6-iron in his hand, base of neck marginally closer to left foot than right. Biily Casper, winner of 3 major championships, top of backswing 3-iron, p83, same book base of neck nearer left foot than right. Jack Nicklaus with his driver same page base of neck clearly in the centre of his feet. Trevino the same, driver base of neck middle of feet, iron, slightly nearer left foot.
In my opinion a possible cause of too much height is that Stewart doesn't get far enough left in the downswing, especially with his lower body and more precisely his left side. Look how the left knee gets stuck, it doesn't get back on top of his ankle until his hands are waist high. Virtually all good players it seems get the left knee on top of the ankle almost immediately in the downswing with an iron at least and then it continues past it. Where the legs of the trousers join should be past the ball when the left arm is parallel to the ground. Stewart's doesn't make it until impact. Indeed, partly accentuated by the forward ball position, the join in the trousers is too far to the right throughout, at the top of the back swing it is maybe a couple of inches to the right of the ball. Hogan Power Golf p142 with a medium iron, join in the trousers right over the ball. The Elk, right over it, Mac's CP six iron on you tube, slightly to the left of it, Snead right over it, Trevino, Weiskopf; Tony Lema driver Ron Watts Historic Golf Shots, fraction to the left.
Stewart, if I were you, with this club, I'd get the ball back a bit, employ a shiftless backswing with the hips and get the left knee moving back on top of the left ankle, whilst holding with the right knee a split second.