Teaching quality glides

Jason Mortimer's latest video reminded me that I had filmed a few of the level 3's doing correct-incorrect glide shapes, recently:

Also like doing hanging hollow holds and swinging hollow holds.

The crunch hollow holds at 37 seconds in Jason's video is the exact way my primary teacher used to have us do them for warm-up- palms resting face up on the knees.  Periodically through the 2 minutes, he'd demand us to crunch up another inch higher.  Having hands face up on the thighs/knees helped us have a visual of how high we were crunching and maintaining position.