There is definitely flexure in there Fred as I was loosing images because of it. But even when the stars are beautifully round there is still movement between the images.
After changing a few things around last night (screw in attachment, shorter subs) I managed to get more keepers than throwers (20 / 20 in fact
) but still had the creep across the page.
Its just strange that I very rarely had this with the G11, but then I wasn't imaging at 2000mm focal length then.