Relaxation is important but I don't think its as bad as all that. The spread looked just fine; and as for getting a break for the double by using your thumb at the back of the deck, well that's my primary method for getting a break and it flies past everybody. The key to making it work under performance conditions is attitude, time misdirection and audience interaction. Tilt the deck back as you get your break in order to mask the action a little more, then hold the break for a few beats while you patter before going into the double. The double itself does need work - I would suggest taking a look at Greg Wilson's "Double Take" DVD for some excellent instruction on the DL. It has to look relaxed, comfortable and natural in YOUR hands.
When performing for a camera, these aspects become harder to manipulate which is why you will recieve a lot of critisism for this kind of technique - but performing for a camera should really be the least of your concerns!
As far as the actual trick itself is concerned, I think the sleight that you use to control the selection initially is a variation on the Load Up Move originally by Wesley James or perhaps closer to the Interlock Principle which Dai Vernon did a lot of work on. Its a great and very versatile concept that's fun to play with. If you like this kind of effect I would suggest looking into all the variations of the "Everywhere" plot that are floating around - one of my favourites is published in John Guastaferro's Second Storm (lecture notes or the DVDs, its on both). Absolute stormer of a trick.
Well done, and keep on working!
David.
