I'm kind of interested in this too. Would this work if say I booked a non-refundable fare combination pay with miles and credit card, then kill the reservation within the 24 hour window, since we do have the option of canceling a reservation within that window with no penalty and a full refund?

Edit: Never mind. I went back to the first page and read about the Risk Free Cancellation policy, where that's the except that the miles will get redeposited. I guess I would have to like for a refundable fare to get this to work.