Could it be this?
"Other changes to the camera setup for Auto Focus
On the fourth AF sub-menu, I changed “Orientation linked AF Point” Press the Set button and scroll down to “Separate AF Pts: Area+pts. Press set to chose this.
This allows the AF Points to be separate when in horizontal or vertical modes. Which means the active AF Point could be at the top of the frame for vertical shots and the active AF Points in the center of the frame for horizontal shots.
Also, this means I can have different AF Areas Selection Modes active. I could be shooting Snow Geese in a horizontal orientation and have the camera on Zone AF, then switch to vertical, have the active point at the top of the frame and be in AF Point Expansion (4)."
If so, more info here:
http://www.timboyerphotography.com …s-and-flight-photography/