Spitfire Gunsight adjustment?

[SEE]

I use my shoulder straps before pressing the trigger. I have noticed that weapons are more accurate/effective when 'strapped in' . It's a worthwhile observation you make as I read sometime ago (before CoD was released) that being 'unstrapped' would incurr penalty and now wondering if that also includes gunnery/accuracy of sights now that you have quoted the manual.

when you loosen straps to get closer to the hud and reticule its still subject to what FoV you are using. i fear the problem is rendering the world differently at different fields of view. but i know that makes no sense. so what is going on.