Hi Graham,
So your choice might be the AptusII7, I don´t know why they say 1.1sec/fr in the spec list, but also say: "The Leaf Aptus-II 7 camera back has a sensor just as sensitive as the Leaf Aptus-II 10, with a capture rate under 0.8 secs/frame, and a sustainable burst of 60 full res images per minute - the fastest back in the industry." This is more what we feel, using the predecessor, the Aptus75S. A great back for use in fashion and still photography. Very nice skin colors, a lot better than the 22MP regarding moiré, no microlenses, live view, excellent for tilt and shift with LF, too. Considering the recent price also very attractive.
Regarding the sensor size of the AptusII10, we also thought so in the beginning, but working for POS in portrait mode or double-page campaigns in landscape mode we often find the longer ratio very useful. Even for standard work we don´t have a 4:3 but longer ratio here in Germany. Of course I would love to have a complete full frame though.
Just my 2ct.
Cheers, Ulf