I went back and tried to test my 90mm f2.8 Apo-Skopar lens using Fred's convention for testing yesterday, but fouled up 1 or 2 of the image when the light was harsh and contrasty. I went back this morning and ran the tests again outside my kitchen window under cloudy conditions. I did the best that I could and focused deep into the image near the upper third so, focus was not in the center of the image. Since the conditions were as they were, I conducted the test tripod mounted at ISO of 200 with using my Markins Q20i head along with a RRS rail and some back to back Promedia clamps that allowed me to mount my A1 and my 90mm Apo Skopar both right side up as well as upside down. I made sure not to bump the lens focus when performing switching the camera in the upside down position on both sides of the rail. I had to swing the camera and the lens and adjust the tilt as one would need if the camera were hand held.
Below are my results, but since the focus was taken it where it was there may be slight advantage to some of the images. One corner or side may be slightly softer than the other (s). But, I think that my copy is centered or quite close.
