Hi Syed,
Your ergonomic holders look great, a very interesting video indeed!
This is how I currently hold my oblique pen.
Relatively knuckles up, but with a bent index finger, and the thumb a bit high up the staff. Today I experimented putting my thumb against the flange, and the amount of control gained was massive. Not sure where to leave the end of the index finger though. It seems to rest on the edge when stretched. Alternatively I could place it on top of the flange but that isn't really ideal either. Maybe I should carve myself an ergonomic holder too. Or not worry about a bent index finger.
Anyway, your videos are wonderful, thank you so much for sharing, and please keep them coming!