Thanks for your reply.
Eventually, I chose optical sight wherever available, for the reason that I tend to get confused between various iron sights in view (I mean those on top of deck machine guns), or have problems to "detect", in the excitement of a dogfight, the radiator cap when it cross the target, among all the "protuberances" on the engine. The optical gunsight, instead, can't be confused. In addition, like in reality, it does not require a perfect alignement: bullets always land in its centre, also if misaligned. OTOH, it has annoying reflections when sunlight hit it from rear. Moreover, as you too mentioned, I sacrificed some historical fidelity making this choice.
And overall its a reall really big #%&*$# to get the tube site set up as the default controls dont work the way they claim in the manual.
Sorry, I don't understand what you mean...