My f/6.3 allows no movements on 8x10. With the lens centered and focused at infinity, the circle just makes it. There is a tiny bit of light out past the corners but it's not useful...the image goes from sharp to smeared very quickly.
It is a great lens for 4x5 (and 5x7, I'm sure)...razor sharp. It's the only lens that makes every trip with me when I'm shooting 4x5. It only comes along with the 8x10 if I'm going to shoot objects close to the camera.
Best of luck.
Dave