When I went looking for a cover for my truck, I was dissuaded by the store owner from getting one of the roll-up type hard covers. Reasoning was that if the box for the cover got banged up, the cover would be inoperative. And they, along with the hard folding types was expensive. I settled on a Laredo soft cover. The side rails have heavy duty velcro down their length that the cover attaches to when you roll it out. I simply lift and tug the cover along the sides to make sure it's tight across the width. Adjustable tensioning keeps it tight, and two sliding locks at the gate to secure it. The aluminum tubes that run across it to support the cover are easily covered with foam insulation tubes to take some of the flap out. Unfortunately, it's either fully closed or fully open, so if I'm pulling the trailer, only "weatherable" items go back there, or they're in covered totes and secured. That has not been a big problem. When rolled up to get the hitch, it does obscure it, so I epoxied a couple of round rare earth magnets in the end of a piece of 3/4" PVC pipe. I set that on the hitch plate and line up with a decal I put on the pin box cover. When the pin box is lined up and reaches the hitch, the pipe gets knocked into the bed, and it's a done deal. The Laredo cover ran about $500, similar to the price of the GMC dealer installed soft cover.
I do miss the sectioned hard covers I had on my Avalanche, though. Too bad GM didn't offer them on all trucks. I could stand on them without a problem.