I just wonder how do you look at your wingtips for example when you're doing rolling scissors or other manouvers which include looking mostly upwards from your simulated cockpit.
I don't...I'm watching my opponent and checking 6. I know from experience that if the stick goes left I need to press left rudder. How much rudder depends on how much aileron, IAS, etc. With experience and practice you reflexively fly the airplane doing your best to keep the ball in the middle. Does it stay centered? Oh heck no, at least not for me. I did tonight tend to watch it more as I was flying just too see how well I do....I do a pretty good job of keeping thing coordinated but still room for improvement.
Keeping the airplane coordinated/trimmed reduces drag. Flying coordinated will only make a small difference in performance but if fighting an evenly matched opponent it could possible make the difference that allows you to win the fight. The way I fly I can use all the help I can get.