Sorry to bump this but i found a workaround. I don't know if it has been mentioned (i didn't read the entire thread), so apologies if it has been already mentioned.
For starters and obviously enough, if you're using a head tracking device you can set your center position to be offset and get rid of this issue: just move you head left, press your centering key and when you move back into your usual center position your view will be shifted to the right, giving you a nice view of the gunsight.
However. even if you don't have a head tracking device there is a solution to this. Turn off the mouse cursor to get the mouse to work as a camera controller (default key for this is F10), keep the right mouse button pressed and move the mouse around: you will see that you can move the camera forward/backward/left/right.
Alternatively, you can keep the mouse cursor on and follow the same routine but with the middle mouse button also pressed: middle mouse button acts as a temporary "over-ride" that disables the mouse cursor and enables camera control for as long as it's pressed, so that you don't have to keep switching between clickable cockpit and camera control all the time.
This way you can set your default viewpoint to be aligned with the gunsight. I think that pressing the "center view" key (default is keypad 5) will not reset your view changes as it only applies to the pitch/roll/yaw axis of head movement (it even over-rides freetrack in that respect, if i move my view to the right it stays there until i manually move it back with the mouse, i don't know how it works with trackIR though).
This way you can fly with the 109 gunsight centered no matter if you use a head tracker or not, it's like setting up your viewpoint to have a permanent lean to the right
