This picture is just after cutting the port hole for Maggie to have her head out of. I spent a fair amount of time agonizing over exactly how high to make this circle. I measured her sitting and standing and eventually used a piece of thin metal that was cut to a perfect circle on the cnc router as a template to make my circle on the curved surface. So I bent the thin metal around the shape of the trailer and traced it. Then used a jig saw to cut the circle.