Comments please?
Mine looks like this - so just from the photos which can be a little misleading, I would say that your box is a little high. or it could be that mine is low, or the photos are not easy to see. What is the angle of the rear flange now?
I know you have probably done this, but is the car sitting flat? The inner sills should be at 0°. How is the box suspended? If it's on a jack the angle will change when you hang it on the car because of the weight.