Hi Tomlin!
I am really sorry for delayed reply!:(
The software used in the mentioned glider simulator is Silent Wings
http://www.silentwings.no/
I haven't had the opportunity to test it but it looks very good to me.
The Horizontal Span view is worth testing. I have been using it for 3 years in my 2x21" CRT screens (2580x960) with Nvidia 8800GT 512. It runs about 30-60 fps my FS2004 setup depending the scenery almost all settings maxed. The Horizontal Span view "behaves" just like single screen with TrackIr 4 and Free Track when I use the VC in the Full Screen mode (no frames visible). I don't know how it works in the FSX. I am sure it is possible to run two beamers in the FS2004 with The Horizontal Span view as well.
If You have Nvidia GPU You will find all needed functions in the Nvidia Control Panel - something like multimonitor setup and so on. Try it!
I hope this helps!
Timo