Everyone I have a quick question... I’m sure it’s been said just maybe I’m not searching the right key words.... Anyways.. what do you guys use to fill in the low spots in the celing so I can apply a flat sheet of plastic to cover my celing. My bus is stock roof height so I’m looking to gain every inch I can... I was thinking some 1/4 foam sheets? Glue those to the metal, and then my plastic sheeting to the foam? What are your thoughts? Prefer if I can go buy it at Home Depot... thanks!