With a square face angle at impact and a neutral swing path, a heel strike with a driver will produce a slice due to gear effect won't it?
Obviously inconsistencies in face angle and swing path may exaggerate or mitigate this in the resulting ball flight, but the theory is sound for a completely neutral swing as far as I can see.
He seems to be making a couple of points. In broad terms what I took from his article was...
First is that the rule that almost all (85%) of the initial direction of the ball flight isn't nearly as reliable for modern drivers as people might think. As I understand his analysis this is because the centre of mass is further from the face. I suspect that the rule is more reliable for irons than for woods but he doesn't really deal with that point.
Second is that the differences in the way the ball deforms on impact suggests there is another neglected factor. In particular when the ball is struck off centre the club will change its path enough to cause the ball to have a path slightly the other way.
As I understand the gear effect it neatly explains heely cuts and toey draws.
Oh, and the high speed videos of impact were fascinating. Just watching the balls deform was great. I'm sure that the manufacturers are very much on top of this sort of thing.
Edited by Forrest Gardener, 12 February 2019 - 12:18 PM.