We did a couple of before-after swings. The thing the instructor changed was my set up. My before set up was a bit too vertical, without any spine tilt away from the ball. Also, from the top view, my shoulders were very open and my feet, knees, and hips very closed. We equalized this a bit. The result was a slight increase in club head speed, a shallower angle of attack and a bit better ball flight. He honestly didn't get into much detail or share much of the remaining data. I agree that there _must_ be a bunch of flaws in there, but to be honest he didn't point much of this out to me.