OK, I have been playing around with this.
Here's the thing, magicians know the method and laymen don't (they prob don't think we would go to the length we do to use something like this)
It works really well with the correct presentation, i guess some of it just comes down to audience management and an entertaining performance.
Some magicians have worked it out and some have not. But more important not one laymen i have tried this on seems to have even come close.
If you are not out to fool other magicians then there should be no problem.
(I'm pretty sure its only us that has taken that much notice of the Christmas cracker thing anyway)