I haven't read your routine for, "On the Up and Up" (where is it published?)so I don't know if the following comment is relevant for your routine ... But
The original Fred Robinson move is performed with your left hand in a different position than that used by Ray Grismer.
Fred Robinson's routine, published in Pabular, has the cards held at your fingertips. This makes the move MUCH easier to perform.
For Fred's routine, you only have to hold the deck using your Thumb and Index finger. This leaves your pinky free to easily reach the outjogged corner and it is also easy to move your other fingers out of the way during the move.
By contrast, in the Kosby routine, the pack is held in more or less standard dealing position. This means that your pinky has further to travel. It now has to curl DOWN to reach the corner in the first place. This is, IMHO, what causes such a cramped feeling when trying to perform Ray's superb routine.
Like yourself, I have only ever seen a couple of people that can actually perform the move well enough to use it under fire. That is Ray Kosby himself and Marc Caplan from Scotland. I have been informed that Paul Wilson also does the routine, but I have yet to see him perform it. Maybe I'll ask him to do it next time I see him :-)
All The Best,