You guys can find the "default" head position, at least horizontally, by panning your view, while parked on the runway and putting the "O" in "auto take Off mode active" dead center in the seat.
Then... tinker with the vertical and set THAT spot as your default head position. When you need the gun sight you will have programmed that to a hotkey somewhere.
Compare how often you're using the gun sight or even the guns vs viewing outside your cockpit?
I set a "true" pilot view in all of my planes for the default view. It pains me to sit behind the gun site in the Mossie Mk IV (and many other planes) when it is so obvious that the pilot naturally sits to the left and his head position is higher. A few planes I dont bother with because the sights are so close to the natural head position.