I am padding barnboard window valances throughout the house-different sizes. I'm starting with the sliding door one that's 8' 51/2" long, 8" deep and has a lip over-hang of between 3/4 to 1". I know I need foam, batting and the material. How do I do this and have the corners look good and not all rounded or bunched? Should I pad over the over-hang or just up to it? I think it would look better if the whole thing was covered. I've never undertaken a project like this. any help is appreciated! Thank you!!