I have a 1970 Chevelle SS, in which I am in the process of replacing the door panels due to faulty weatherstriping around the top of the window. I know that the top of the new door panel fits in the grove where the window goes up and down. And that the sides use the three panel clips and plugs on each side. But how is the buttom attached, there are no mounting points on the door shell or on the new door panel from PUI, Inc. Anybody know the answer? Thanks a bunch.