I find that compressing the Xplane window to half the screen distorts the vertical movement.
I use Xplane at full screen (but still windowed) and adjust the view with the right mouse button so that the horizon is 3/4 way up the screen. Then I just put PSX in the lower half of the screen, on top of Xplane. Hope that makes sense.
You can save an Xplane view by hitting Ctrl+Numpad(x) once you're satisfied with the view. In Xplane 10, just hit that numpad number to recall the view. For some unnacountable reason, in Xplane 11 you have to hit numpad(x+1) to get the same view. Or, if you like, hit Ctrl+Numpad(x-1) to save it.
For instance, I use numpad 5 for my default ahead view. In Xplane 10 I save it by using Ctrl+Numpad(5), but in Xplane 11, I use Ctrl+Numpad(4)