it's true that if you put regular bags on expanded metal flooring for any extended period of time that the expanded metal will destroy those bags, but that's why you get the bags designed to go on the roof (made of much more resiliant (sp?) material) or cases (such as pelican or gator, etc...) for the rack you should be good to go. Personally I don't like crossbars because there are certain things that would lend themselves to being placed up there...like shoes