Best D3 setting for motorcycle race...metering, servo, AF etc..
I have found that 3D autotracking works for well for people as long as movement isn't too fast and erratic, so when I'm shooting kids I shoot in 3D mode and find that I can use the 3D tracking to make different compositions while the tracking remains on the person. I have found long lock-on works best for me.
As soon as things speed up, I switch to my Action program and use 9 point AF, with short Lock on. After reading this, I might try without AF lock.
I also wondered whether 9 points vs 21 points would make a difference in taxation of the AF system, so I erred on the safe side and chose 9 points. Also, when using the center point (for birds) you get 9 cross-type points. Works well for me.