I looked at a mustang today and a guy has rust on the inside of the roof of his car that he is stripping down to be restored. It's a late 60's mustang has rust with insulation stuck to it. He figures it was in a high moisture environment and water must have condensed up under the head liner. Soda won't take the rust out so I could use glass but it's thin metal after the rust comes off don't want to warp it on the other side of the upper quarter panel and roof. What about walnut?