Yes. In order to get f/8, I tried two options.
a) 70-200 2,8 + Canon x2 + Kenko 1,4 pro 300
b) 70-300 DO 5,6 + Kenko 1,4 pro 300
Both did AF well, and not only whith the center point.
And the good news is that it still works with firmware 1.06
Unfortunately, I don't have an adequate lens to check whether it would also work at f/11