Rose wrote:Yes... but you may be restricted to centre focus only.
I wondered if that might be the problem. It depends on what the maximum aperture is on the lens, so the 70-200 f/2.8 + 2x extender would mean a maximum aperture of f/5.6. The combo would be slightly heavier than a 100-400 Mk II and there is the loss of up to a stop at the shorter focal lengths which would start at 140, but it would still be able to use all the AF points. With the f/4 version of the 70-200 as the starting point, you would be restricted to the 1.4x extender to retain full AF functionality of course.