IAIN beat me to it, but I'll back him up on the suggestion of the `deeper cut` force.
It's nice and simple.
HOWEVER - I personally would stick to the cross cut - why?
Because for me, when I've watched magicians and they ask me to pick a card in a un-natural manner involving strict instructions, it takes away the effectiveness from the trick, because you instantly know its something self-working, it's common knowledge. (this goes back to before I was a magician)
You want a force, that stays as close to a -real random card pick- and by asking a person to cut the deck, for me comes across as the most natural hands-off card force I have seen.
However I have not researched much into the amount of hands off forces out there, but I hope my advice helps you anyway
