I was putting a slant roof on my coop, but I have all 4 walls the same height. It's a 4x8 coop and the walls are 4 ft high. The top edge to where I would attach the roof are 2x4's skinny side up. Is that enough surface to attach a roof to? Do I need to lay down more 2x4 on top to the fatter side is up? Also I wanted to be able to move this around, so it's on wheels. Whatever roof goes on has to be lightweight, but strong. I would hate to dismantle it to make a side higher. Any options or ideas are much appreciated!