Thanks Tyler. I've been continuing to practice this week, and wanted to share 3 videos with you if you don't mind taking a look:
1. The first video was taken at the same time as the original down-the-line video from earlier in the thread. Again my focus was on eliminating early extension, and like I mentioned, I was able to get occasional strikes in the center of the face, but the contact felt weak. I feel like your initial hunch about ulnar deviation as a reason is correct, because I could kinda feel like I was holding onto the hinge as I was coming into impact. Hoping this face on video might shed more light on it.
2. The second video was taken the next day as I started to think about ulnar deviation and try some experiments with new feels. On this one, I tried to feel more active ulnar deviation just after transition while rotating my body through impact. The hits "felt" very solid, but I experienced what I usually feel when I try to actively unhinge down, which is I feel myself coming out of my posture again and my hips start swaying forward and tilting. On video it looks to me like I have no shaft lean either.
3. The third video was taken the following day, and here I just tried to take a more passive approach to ulnar deviation, and just let my wrists be loose. On my backswing, I tried to avoid hinging (cocking) my left wrist while still doing the motorcycle, which felt to me like "starting" with my wrists closer to an ulnar deviated position. Then from the top, I focused on bringing my elbow in front of my stomach while keeping my wrists loose. The whole swing felt much wider and the follow through felt especially wide, and I was able to keep my posture (axis tilt) without early extending. The contact felt very solid, and on video I can see more shaft lean than #2.
#3 feels like I'm on the right track, but would like your opinion on how I'm approaching ulnar deviation. I saw your video on ulnar deviation check points, but I can't quite tell if I'm getting it right. So would appreciate your view on what you see in these videos.
And yes, I'm in the witness protection program for snitching on some serious criminals, but I'm willing to risk putting these videos online in hopes that I can improve my swing.