What screens are you using for passing information for cockpit displays?

Hey,

We have been trying to use a 15" display but it just won't work at passing info from fsx for the GPS unit from reality xp.

So I am wondering what screens is everyone using to display the GPS, or any other screens for fsx (aside from main screen). I'm hoping to find an alternative to the 15". I'm suspecting the problem with the 15" display is because it's
a different aspect ratio, as it won't work on a 17" of same 4:3 aspect ration either. However it will work on a 22" wide screen. However that's a bit too big for just a GPS.

Has anyone tried 18.5" Widescreen LCD's for the GPS in fsx?