neuroanatomist said:
I believe that the AI Servo parameters (tracking speed, focus priority, etc.) can be registered, but not the AF mode itself - that seems to be what the manual indicates. It states, "Convenient when you want to change the AF characteristics duringAI Servo AF, not to AI Servo AF. However, I haven't tried it yet.
Ok, I just tried it, and no, Switch to Registered AF Function
does not change you from One Shot to AI Servo.
Still, that combination combined with the one-button press-and-hold change to AI Servo would do it, i.e. assign the registered AF function to the DoF Preview button and use that for a one-touch change from single AF point selection to 61-point auto selection, and then press and hold the M.Fn2 button to change from One Shot to Servo. Obviously, that's only possible on the 1D X with the M.Fn2 button right next to the DOF Preview button.
Still, I currently have C2 assigned as One Shot with single point selection, and C3 as AI Servo with 61-point selection, and I can rapidly switch since I have the M.Fn1 button assigned to Switch to Custom Shooting Mode. That's better for me, because in Servo mode I also want a higher minimum shutter speed setting.