Ideally your spectators should be directly in front and to your right, this isn't a move that can really be done surrounded, there's certainly more appropriate colour changes to use if you are surrounded. You might want to look into Pughe's pass on Dorian Rhodell's Avenue (You might be able to find the original write up of this move but I can't remember where it is). It's very similar and gives you slightly better angles, it feels a bit more natural to me as well.
As for the right hand position, I cover about half the card as I do the snapping action, as soon as the top card is clear I straighten my fingers so my index finger is nearly at the edge of the card and my thumb is along the bottom edge, this covers the change but also appears quite open. I think that's how Dan and Dave perform it.
Well , in my opinion if you do it correctly, with the right move, the right timing/speed and the right coverage , you can do it from almost all the angles with no problem, i've been performing this change for a long time and never I saw somebody seeing it or saying that saw it.
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stluiz1
I'd be interested in knowing how you can cover it from the left, I don't see any real way of doing it, they're going to see a part of the card above the deck or below it. The right hand offers no cover from this angle at all unless you press it right against the deck, which is going to prevent spectators to the right seeing it properly and looks strange. They can also see the left fingers holding the card under the deck. If you worked out how to cover it from this angle i'd really like to know how,