There is a [Dynamic Head Movement] section in the FSX cfg. file
[DynamicHeadMovement]
HeadMoveTimeConstant=1.000000
LonAccelOnHeadLon=-0.020000
LonAccelOnHeadPitch=-0.010000
MaxHeadAngle=5.000000
MaxHeadOffset=0.300000
RollAccelOnHeadLat=0.010000
RollAccelOnHeadRoll=0.100000
YawAccelOnHeadLat=-0.100000
I imagine some fiddlin' with the values will get the desired effect

Edit: Unless Track IR overrides these values???