I should add that I'm continuing to practice with this new found awareness of the retarding of rotation of the high side while the high side mail-slot fingr-tip entry occurs, then rapidly (not forcing, just sling-shotting) snapping the rotation into action (maybe with the help of the stretches lats muscle on the high side). I'm experimenting with getting the low side arm catch starting a little earlier, different from my prior focus of being very patient with the lead hand to a fault.
The earlier catch is a little tricky as it starts to get earlier past a certain point -- I had spent a lot of time learning to delay the catch until I had rotated that low side to the high side, and I learned it so well I'm having trouble unlearning it. It seems to throw my new-style (of the past 2 years) balance equilibrium off, but I'll chip away at it. I'll play around with the kick timing too.
So far, it's still early days. I find that I'm not tiring quite as much as I do more repeats -- I'm really trying to do this with a focus on relaxation. I'm not getting any faster yet (or, rather my strokes on a constant TT timer beep still seem to get progressively shorter as I fatigue, but I'm lasting longer, with more repeats possible even at this early stage, so I'm quite encouraged).