[EJGr.Ost_Caspar]

Thats the funniest footcam of WW2 I 've ever seen (the guy that gets blown away).

To me this small timeframe, where you can see the pilot, tells me following: There is no much space to move upward. Pilot can definitly move his head quite a bit, even if he is strapped. Its even easy ergonomical testing, which I can do at home - without moving my upper body, I can get my eyes near the line of my shoulders, although I cannot keep my head straight horizontal, but have to bank it. I also can look directly behind me, but again not straight and with one eye only.

But I think this is all well clear - the fixed 4DoF is as unrealistic as the 6DoF in mods is.
I say the kind and ammount of movement in a WW2 airplane, no matter which one, is very restricted (with the Bf109 being a very narrow one). And a 6DoF solution has to be like this.