
The cutting of the cards is a bit of a wheeze. When the cards are all collected back together again, the 3 cards will always be in positions 10, 26 and 42 in the deck. Then when you're doing the Up Down bit, you change the order on the 2nd deal and it should all work out from there.
Used the constipated mathematician's method here i.e. worked it out with a pencil.
I need a drink.
( , Fri 6 Jul 2012, 15:11, Reply)

The cuts are genuinely random, but when the piles are re-stacked, the cuts are effectively reassembled and the 3 target cards will always be in positions 10, 26 and 42. The rest is showmanship.
( , Fri 6 Jul 2012, 14:52, Reply)

then it's exactly the same number of cards and the aces haven't moved.
( , Fri 6 Jul 2012, 16:51, Reply)

Pile of 15, Pile of 15 and finally Pile of 9.
Puts the ace on top of pile of 10... that's now the 11th card from the back of the pack.
Cuts the 15, hides Ace in the middle of the cut, BUT ZOMG NOT REALLY, 'cos then he just places the second half of the deck back on the first, so it went from
1, 2, 3, 4, ..., 15
to something like
10, 11, 12, 13, 14, 15, 1, 2, ..., 9
Still 15 cards with Ace as a 16th.
Basically, the cards never move away from their predetermined positions.
Watch it again and you'll notice he fiddles about with putting one cut deck on top of another, etc., but the groups 10-Ace-15-Ace-15-Ace-9 still remain. This is in reverse order, so when 'dealing' the deck it goes rather:
9-Ace-15-Ace-...-10
Or, Aces at 10, 26 and 42; which then enables the magic of the continual half and half dealing until ZOMGZ0RZ IS MY CARD, OH MAGICIAN, HAVE MY BABIES!
( , Fri 6 Jul 2012, 20:51, Reply)