This is my first post on the forum, but I've been an active reader for over a year.
A bit about my history. I'm 35 years old and have been playing since high school. My game peaked during graduate school where I was regularly shooting in the low 80's, not uncommonly in the high 70's. I never calculated a handicap unfortunately. In the intervening years I've been able to play less and less due to work and family considerations, and I noticed deterioration in my swing consistency and ball-striking, where I was previously very consistent with my irons, if not challenged for distance. Looking back, I think I've always had a bit of outside-in and have had difficulty ending up with my "weight forward" at impact.
Last year, when I found this forum, I attempted to adopt the SnT system, bought the book, hit the range and all of that. I was self taught, as a certified instructor was not available in my area. The reasoning made sense, but I was never able to transtlate it to consistent ball-striking. In retrospect, I was probably putting too much "weight forward" and overly lowering my head over my left knee, and doing some unnatural compensation just prior to impact. I have to say it felt pretty awkward, and gave rise to the longest string of shanks I've ever experienced in one round!
So after a long hiatus, I decided to revisit my swing mechanics and visit the forum once again. I must give Erik and David kudos for collecting some objective data, making a break from SnT dogma in light of new evidence, and developing a seemingly improved system based on that data. Importantly, you've hit the nail on the head regarding the collection of accurate and reproducible data. However, I think it would pay to revisit the terms being used, regarding weight and pressure. I feel it's a shortcut the way that weight and pressure have been parsed out and defined, making it easy to understand for most, but challenging to come to grips with for those of us with more of a background in the sciences.
The one thing that is constant is the body's mass, not weight! Weight is a measure of the force exerted by gravity on a particular mass. In your static photos at various swing alignments, the pressure plate measurements are truly reflective of the action of gravity alone, the force at each measureable point on the plate, in some unit of weight/area. So why do these numbers change during the swing, even though the golfer's position is similar? You've already aptly pointed out that very little of the change in pressure measurements can be accounted for by changes in gravitational force right-left distribution. So the only explanation is rotational forces which are changing during the swing. As the golfer rotates around an axis in a plane diagonal to the ground, there are centripetal forces at work. The club head wants to fly out tangential to the arc of the swing plane, and the golfer exerts centripetal force sagitally to keep it in place via the grip and shaft. A diagonal plane can be broken down into vectors that are parallel to and perpendicular to the ground. The differences we see on pressure plate measurements are due to the additional force vectors that are perpendicular to the ground, or parallel with gravity. The horizontal vector is of course not measureable by the plates since they only sense what is vertical to them.
In summary, my understanding is that static pressure=gravity and dynamic pressure=gravity + rotational force. Now I'm not nearly smart enough to even attempt to quantify the math such that it fits the data you've acquired. But I think that if you're attempting to take a more scientific, data driven approach to the swing mechanics, you need to use terminology appropriately. It's not just semantics, it's a demonstation of clear understanding of the subject matter, and using terms correctly gives you more broad credibility.
All that said, I watched a bunch of your videos online and hit the range yesterday. I used your soda (pop) bottle drill, the 2-ball drill, and pretended I had a squishy ball under my left foot. I even tried keeping my right toes up a bit on the backswing. A lot of things clicked! My contact was not only solid, but consistent on the club face until I fatigued. Ball-flight was right down my intended target line on the way up at least. I was in a pressurized golf-dome only 70 yards deep, so I could only see the first half/third of the ball flight. I'm heading to Scottsdale in a week and hope to get at least one round in as well as some time on a warm, grass range.