I went to the Moto cross event today as I wanted to try the AFC tracking on the XT2 with both the 100-400 and the 16-55 and I used the following settings:
ISO = Auto
Zone Focus = 9 central spots then wide tracking
AFC category = I used setting 4 (subject suddenly appears)
100 - 400 set to f8 and 1/2000 sec
The above were for most of the images but used f5.6 with the 16-55mm
I am thrilled with the performance and it more than lived up to all my expectations and the only focus fails were down to operator headspace!
These are just a few of the images