If anyone has a Canon EOS-5D MIII and a Kenko 1.4X TC (the top of the line one: C-AF 1.4X TELEPLUS PRO 300) and (preferably) an 800mm f/5.6L IS (or a 400mm f/5.6L) I ask:

Have you used any of the above combos successfully getting AF when you are not supposed to get AF (i.e., at f/8)?