Kenko 1.4x and Canon 400mm f5.6 (1 Viewer)

Attached are some pics taken with my eos760d + Canon 400mm f5.6 + Kenko CA-F 1.4X Teleplus MC4 DGX.
I have found autofocus to be fast and 90% reliable using one of the non-cross type focus points to the side of the centre focus point. I get no auto focus using the centre spot or the cross-type focusing spots immediately to either side of it.
The birds were 10-20mtrs distant.
I felt people who use the Canon 400 f5.6 might be interested in this because the Kenko converter is very affordable, returns useable quality, and 560mm is pretty useful,
regards Pete
PS Can anyone tell me how to turn off the 'smart text' when composing posts here - it is a total pain in the a . . . .e!

I have the kenko 1.4, found it wasn't very good with the Canon 100-400, the kenko does however work with my new(to me) sigma 500mm f4.5 and yet the Canon 1.4 won't work with the sigma. Canon must put something in the connectivity to stop us using some other products. I am using a Canon 1D iv body.

Hello Burnie, I am sure you are correct re. Canon deploying techno stunts to prevent users from availing themselves of 3rd party products eg chipped batteries. This would be fair play if their batteries were reasonably priced but they are not c'est la vie.
Is the Kenko you are using the same as mine? Spec'd in my original post.
Also - how are you finding your Sigma 500 f5.4? They are quite affordable 2nd hand now.
I have just purchased a Tamron 150-600 G2, so far I am knocked out with it (see the most recent three pics in my gallery). The lens is now revealing the limitations of my eos 760d (particularly noise). I am hoping to upgrade probably to an 80d at some point.

Mention of a Sigma 500 f5.4 caught my eye and I decided to look into it. Well, it seems f4.5 was intended. It is an old design, and heavy for its max aperture compared to the Canon f/4 II. No interest to me.

Now if Sigma would actually produce a new lightweight sharp 500mm f/5.4, that would be wonderful.