Normally for cresteds people build custom racks to give some extra height to the tubs. I myself use things like bookshelves, works great for babies, alot you can use shelving units for garages also for the adults as the shelves are spaced pretty far apart, perfect height for taller tubs. But I wouldnt go smaller the a 10 gallon tub for a single adult.
Racks work great for cresteds. Just make sure the container is at least 9-12" high and they'll do fine.
We had these racks custom made by Animal Plastics. They hold a 66 quart container. We also have some racks that hold a Sterilite 58 quart (from WalMart).