Didn't capture a video since dark outside so can't say for sure if it's a fact or just what I'm feeling but it seems that if the hands don't gather depth by A2, it gets much harder to gain depth later (unless you are Rory).
Conversely once you get the hands even slightly deeper at A2 than address (no club rolling) it gets easier to gain depth further. I practiced this with my shoulder plumb line to floor for check at A2. The ball compression with my 18 deg iron felt really really good. Swing felt shorter with a faster tempo.
So...., low hands with arms unified with torso skate slightly inside of shoulder plumb line when they arrive at A2. Clubhead should sweep but not roll maintaining forearm to shaft angle.
Letting my left arm fully rise to chin after this seemed to make it really easy to transition and honestly to an awesome impact.
Practice was fun today.