I agree. A second gunsight might assume a second button. Shift+F1 is for 'gunsight view' or 'aim view' or what it is called - and here this means for both gunsights - which is the point, that we could have mentioned.
However... IIRC, you can reach that upper gunsight also with 6DoF movments (by mouse or TrackIR) in the normal 'flight view' - so the 'Shift+F1' hotkey is not essential.
I think, the good thing with simulations is, whenever you have a problem, try it to do as you would do in real life. In most of the cases it works.
