I wanted to upload a video today of something I've been working on related to Key #4.
I was experimenting with some feels and discovered that I wasn't turning my hips enough in the backswing. As a result, I don't get enough shoulder turn, and fake it by pulling my left shoulder back. The problem with that is, I don't release the pull in the downswing which I believe is part of the reason I have the gap between my elbow and my body and I can't get enough pitch. I think it's also part of why I seem to have a problem getting shallow.
The first backswing I make is my current feel. See as I get to the top and release all the tension in my left shoulder and arm, my shoulder turn goes from 100° to something like 70°. Then as I swing down, my right elbow is clearly to my side.
The second backswing is where I make a deeper hip turn. When I do the same release, my shoulder turn ends up being around 90°. When I simulate my downswing, my right elbow is in front of my right hip, where it belongs.
I took some screenshots. I want to emphasize that these two "swings" feel the same, with the sole exception being that I turned my hips deeper on the right.
Even more shoulder turn on the right, though it looks like I lost a bit of extension, too.
A4 with left arm released:
This is what led me to believe I was "faking" my full shoulder turn. On the left, when I release the tension, my shoulders open up significantly. On the right, I end up at 90°. These felt exactly the same; I'm not purposely holding anything on the right to make a point*.
* (Click to show)
And why would I, anyway? This is my swing thread, there's absolutely no benefit to faking any position to make a point.
A6ish, it's a simulated swing:
Here you can see how it affects my downswing. It may look like the screenshot on the right is taken at a later point in the swing, but if you see where my shoulders are at, you can tell this is the exact same point in two different swings.
My arms are behind me on the left and you can start to see that I have start casting if I'm going to have a chance at hitting the ball (not pictured, there's no ball). If this were a real swing, the club shaft would actually be parallel to the ground already as I would have started to throw the lag away, and my right elbow would actually be farther away from my body, leaving a visible gap.
I like the swing on the right for all the reasons I dislike the swing on the left. My arms are more in front of me and I'm retaining the lag much better. I'm coming at the imaginary ball more from the inside, too. I know it won't look like this when I make a real swing, but it will be closer to it than the swing on the left would produce.
I should have done a DTL video, too, just to confirm. Even without it, I'm pretty sure that the swing on the right will have deeper hands, and shallower club, and more pitch elbow. I'm sure I learned all of this is in some combination of videos here, but this is the first time I can say that I'm starting to truly understand it and thus apply it to my own swing.