Quote Originally Posted by M_Six View Post
Someone on POTN was asking if the extra sensitive center focus point on the 6D would AF at or above f8, so I tried it out with my 70-300L at 300mm and my Kenko 2x TC (for 600mm and f11), and bigger than Stuttgart it worked! Check the EXIF on this (although it doesn't say AF anywhere, just take my word for it).

More testing to follow, but this could be a good thing.
Keep in mind that the Kenko 1.4x Teleconverters tend to allow autofocus in situations where the Canon Teleconverters will not.