It needs some elastic but that is UNDER the protective paneling. There is a way to design side panels that have an elastic ribbon attaching them to the bottom and back and front panel, so that they flex and you don’t need the zipper that goes all curvy to the back and down… I can draw a cad file or napkin drawing.. but the thing with elastic is that it breaks down over time especially with UV… so you want the stitching and location of the elastic under and inside the outer protective paneling… think armor plates connected with flexible strips.. the future horizontal strip that goes over the hinge, would be connected by a hidden elastic band and the hinge panel would freely hang down so that it can accommodate the ‘compression’ side of the arc that the lid makes.. there either needs to be strong magnet holders for the front flap or plastic buckles so when your driving 85MPH with the cooler in the bed of the truck it doesn’t flap to death.. the Velcro didn’t hold at that wind speed. Eliminating the zipper will save on costs and small amount of labor as the elastic hinging that allows the more rigid panels to move past each other will cost less..
