Having just completed AF fine tuning with my D300/80-400mm/1.4TX I have been putting it through its paces at one of my favourite spots for wasting time in the sun.
For anyone that is using a TX (tele converter) on a long rig and suspects their images are soft or not capturing focus where they expected it I highly recommend checking for front or rear focusing issues. At the focal lengths I want to use with these small subjects I found it was out almost as far as the maximum adjustment possible.
I'm now becoming obsessed with capturing these guys
No 1
No 2
No 3
No 4
Grahame