Is lead an acceptable filler to reform an area of sheet metal that is impossible to fully access? I know the factory used it to fill and smooth seams where some of the body panels met. I've never used it before but it seems like it would be less prone to cracking and rust than plastic. I realize there's no structural strength to it but maybe can be used to reform contours in difficult to get to areas that need a lot of work. I dont really want to lay on that much plastic.