Let me revive this old topic. My tonneau cover also billows while driving on the highway. I tried tying a rope or two over and under but that was a hassle and didn't really work. I tried the pool noodles that were recommended by a few readers. Four of them make no difference and I don't really want a dozen pool noodles at my campsite. I could store other things underneath, but don't have much to store and don't want the cover higher than it already is. In my compact SUV I cannot see over the top of the camper when the cover is billowing, and that makes driving more hazardous as I don't have special side mirrors as if I were driving a truck. I've tried to find some elastic band that I could wrap around the 4 sides to greatly restrict the air that gets under the cover, but I can't find anything appropriate. I suppose I could use several bungee cords hooked together, but that would be hard to do by myself each time I take down the camper. I've even considered the desperate measure of cutting holes in the rear of the cover to allow air to escape more rapidly, but I'm not sure it would work and might cause too much damage. This billowing problem and the frequent need to replace snap fasteners has my wishing there were a better cover for this popup.