Thanks for sharing those. As I also demonstrate in the video, bending the thumb down can create an adequate "V" facing the shooter. As I mention in the video, each individual needs to find what works best for them as an individual.
So much of it is physiology. Things that work for me (5'9ish) won't work for you because you're tall, and vice versa. Same with body shape, flexibility, etc, etc.
I think coaching fundamentals in pool is pretty similar to being a bike fitter: you need to make bodies of diverse size, shape, flexibility all function optimally in the same environment.
