OK... so I've been tinkering with the orientation of the camera to see the effect...looking at the master flats in an image viewer, there's definitely some distinct movement of the shades, and a couple of round spots too.
I've restocked the image with the set of flats that - I think - are least intrusive, there is a wedge on the left of the image that is starting to manifest. Let me know what you think - obviously it's not a perfect situation - I'm just experimenting and learning, and gaining and appreciation of my mistakes
