I had originally put the new section on top of the old one and that is where I saw the big space issues. Realizing I would have to clean the lip to adhere the gasket, I figured I would use the new section on the bottom as the lip was new and clean. Lo and behold, the old unit fit almost like a glove. I am still going to do the gaskets but now I am sure that I will be getting an air tight seal.