I bought this lens recently to replace my previous Canon 300mm F2.8 II and expecting a significant improvement over my existing FE 200-600. I planned to use it half the time at 560mm F4 and at 400mm when the light was low and/or the F2.8 DOF was needed. The bare lens show some decentering bottom right and is not as sharp as I expected at F2.8. With the 1.4x attached it is not even as sharp as my 200-600, even at the same aperture and significantly worse that the 300 F2.8 with a 2x attached. With the 2x attached the images are soft. I would like to have this lens and the 1.4x Extender serviced to ensure that neither has a problem or has been damaged in transit. There is often a clunking noise from the lens, is this normal ?. It may be the IS and also may be the source of the image quality problems.