cbfoulds,
I think my head height is OK and my lock in is working.
This is a frame that immediately preceded the 1st "pitch in the dirt" you reference above.
I "lock-in" when the pitcher "sets" to receive the pitch. I stay in that set, even should the catcher move. I believe in the pics you reference, the catcher has "gotten tall" as part of his blocking technique, and I'm locked in where I started.
JM