"1 monitor" results in generally Vert- gameplay in multi-mon. You don't want that.
"3 monitors" is actually a misleading name; it's actually a "3 camera frustums" mode. The game doesn't care if you really have 3 monitors and whether they are grouped as an Eyefinity display or whatever, in fact you can use "3 monitors" with a single screen. It simply divides the display width in three.

Here's the complete script (C:Program FilesEagle DynamicsDCS A-10CConfigMonitorSetup3Cameras.lua), quite self-explanatory even for me...

Code:

_  = function(p) return p; end;
   name = _('3 Screen');
   Description = 'Configuration with 3 identical monitors each with its own camera'
   Viewports =
   {
        Left =
        {
             x = 0;
             y = 0;
             width = screen.width / 3;
             height = screen.height;
             viewDx = -1;
             viewDy = 0;
             aspect = screen.aspect / 3;
        },
   
        Center =
        {
             x = screen.width / 3;
             y = 0;
             width = screen.width / 3;
             height = screen.height;
             viewDx = 0;
             viewDy = 0;
             aspect = screen.aspect / 3;
        },
   
        Right =
        {
             x = screen.width * 2 / 3;
             y = 0;
             width = screen.width / 3;
             height = screen.height;
             viewDx = 1;
             viewDy = 0;
             aspect = screen.aspect / 3;
        }
   }
   
   
   UIMainView = Viewports.Center

Unfortunately this mode would be ideal for square panels at a 45 degrees angle, and is slightly weird in TripleWide (mainly because you may see both wings of your plane when you shouldn't). My screenshot however, with the "broken" horizon line, does not do it justice: look up a little, and it's fixed. Give it a go ! ;)