OK, made a little progress.
1. I got head tracking working by selecting 'FSX SimConnect' under FaceTrackNoir's 'Game Protocol' section. I also had to invert the Pich axis under the Axis Inversion section (for safety, do the axis change when FTNOIR is 'stopped'...I found that if you changed it while running, it didn't take affect in FSX).
2. New problem: I get head tracking (minus roll) in the cockpit, but now the left stick on my XBox controller doesn't work.
3. The right stick still works for virtual cockpit view, but it's annoying if you accidentally move it because it messes with your current head-tracked view.
4. Running at 1280x800 gives a nice framerate, but it causes the ugly vsync tearing problem. I'm gonna turn down FSX's detail setting so I can run it at my primary display's native resolution (1920x1080)...this eliminates the vsync problem.
EDIT: ignoring the lack of XBox left thumbstick operation (a pretty big problem, granted), it works pretty good. The view inside the cockpit is a bit disorienting, though. It feels like the cockpit is rendered through a fish-eye lens, causing everything inside to be somewhat distorted. It's good, but it's not great (like, say, the view inside Heli Hell's 'copter, or First Law's spaceship cockpit). Also, it took only about 10 minutes of flying for the Rift's yaw drift to become obvious; I ended the flight with my virtual body sitting 90 degrees to the instrument panel. I had to keep my head turned 90 degrees left to be able to look out the wind screen.
EDIT 2: Roll works.