I got everything working last night. Occasional crashes aside, I'm having a blast flying around in my Rift.
One thing I noticed is that the head position shifts forward and back slightly with the throttle position. Maybe it's an acceleration effect, but it breaks presence for me and means I'm constantly re-centering my head position.
Is there a way of disabling this motion in the game settings? I'm new to FSX so I don't know where I should be looking.