How to Change Resolution for Widescreens?

[Igo kyu]

Does this mean that with a rotatable monitor I can have 1200x1600?

[Feuerfalke]

Yes, 1200x1600 works great to be honest.

Infact, since the sides of the cockpit are the limit, not a given field of view, you will lose the upper and lower part when switching from 4:3 to 16:9 or 16:10.
Mirrors will require you to look up, while you can see them normally on 4:3-monitors.
On the other hand, when using 1200x1600 you will gain additional portions below and above the normal field of view, so you can even see the mirror when in normal view or when looking through the crosshairs. Same is true for instruments, of course.

It's up to your personal preference, but I recommend disabling resizing on your monitor and then choosing a 4:3 resolution. This way you will have black bars to the left and right, but a rather large field of view.