Jim from BeastSkills.com shows some of his Reverse Muscle-up aka ‘Elevator’ training. I like the idea of using two boxes (instead of unstable rings) to learn this. A beastly upper body Pull / Push exercise.
Richard Burnze got them on lock.
Here is Johnny Sapinoso doing a nice workout. I have never seen a knees to elbow handstand walk… Also check out his ring strength. Getting stronger every time.