This has become my new favorite trick. It blows away the lay audience, which is all that matters to me.
Although you don't end clean, and the gimmick is still in the deck, the fact that you let the spectator shuffle the deck before starting helps and the ending is so strong that they have no clue how it is done and in the dozens of times I have done it, no one has ever asked to examine the deck.
Although I would not recommend doing this, just for fun I have repeated the effect two or three times for the same audience and they never get even suspect how it is done. They are simply dumfounded.
