I had a tonneau cover with a vented gate for almost 10 years. In the off season the regular Tgate was put back on. I never, ever saw the tonneau cover balloon while driving. I have a tonneau cover on the truck I have now but don't use a vented gate because it's too much of a problem to take the present gate off(Rear view camera). If, when driving with a tonneau cover on, you look out the rear view mirror, you will notice that the air moving over the cab will push down on top of the cover. The cover prevents pine needles, leafs etc from getting into the box when parked in that environment. IMHO, get one.
