Your Diamondback cover a SE or HD model? I kicked around the idea of having a rack for a RTT built on the cover, I got the SE model. I figure if I keep all the load bearing portions along the edges of the cover I can get away with exceeding the load rating on a static load by a factor of 2.
Mine is the HD model. This setup works great. Keeps tent below roofline, still fit in parking garages, bedside under Diamondback cover makes for easy access, Frontrunner Wolfpack boxes fit between rack and bedcover if I need more space.