I $50 tricked at Bally's last Septemeber. Upgraded to a beautiful, massive suite for the five days of our stay. Will be trying the same at Venetian, Luxor etc this November. Worst case scenario you end up losing your 20/50 and get no upgrade. Even if the clerk says no, who cares?! You'll never see them again. If you don't ask you don't get. Phil