actually that is not a great idea. First, you can cancel w/ 24hrs on a paid ticket only if it is from co.com. If you bought it over the phone you are out of luck (you can still put an int. on hold over the phone).

second, even if you were able to cancel. the upgrade seats would go back into the pool and someone else in that time could grab them.

third, if you are granted a upgrade and then cancel the ticket you loose the upgrade fee (the fee is nonrefundable).