I'm curious if the depth of the cover has to be a certain depth. I'm thinking no but, thought I would ask anyways. The covers I'm making are 2" deep. I have scrap 3/4" solid oak shelving that I was going to use for the top under the tin. I'm using all-season in inner covers so I was keeping the outer from covering the screened holes. I can go either way with the 3/4" on top of frame or inside.