Everyone is different, but I would cap it and make sure it's fully sealed for weatherproof, then put a rack on it. My reason for weatherproofing is due to dust/dirt/sand/rain and less worries of things falling out. Also saves you the time of not needing to secure/tie everything down. Open the cover, throw your gear in, and move on. And when the bed gets dirty, put down the tailgate and rinse it off with a hose.