From my Marriott credit card, I have the annual free night certificate at a Category 1-5 property. The certificate expires in late October. Between now and late October, I will be visiting Sydney, Australia, where I would like to stay at one of the Marriott properties overlooking the harbor. However, both properties there are higher than Category 5. Is it possible to use the free night award at these higher end properties by supplementing my own points (or cash, even) to make up for the difference, or to "trade" the free night award for the 25,000 points (value of Cat 5 night) so that I could then use those 25,000 points plus some of my own points to pay for the stay?