Fuel

See the Multi-monitor method below and input these values:

2560x1080 — 04380A00
3440x1440 — 05A00D70

Registry edit required.

1) Launch the game once to adjust Video options to your liking. You can then Quit the launcher app.

2) In regedit, navigate to
HKEY_CURRENT_USER\Software\Fuel

Edit the VideoResolution value.

5040x1050 : 41a13b0
3840x800 : 3200f00

3840x1024 : 4000f00

3) Launching the game through GameSetup.exe seems to override any manual registry edits. So change your shortcut's target to SecuLauncher.exe or you'll be back to a single-screen res.
If you ever need to run GameSetup later, don't forget to re-edit VideoResolution in the registry afterwards.

To improve visual quality, you might want to disable Shadow Maps in Surround resolutions. To do so without using GameSetup, simply enter 0 as the VideoShadowMap value.

Beyond a 16:9 AR, the HUD is affected in a number of ways (top to bottom) :
-the compass kind of inflates (big letters) but is fully functional
-the 'smart GPS' (flying red arrows) scales correctly
-the timers' and opponents list's frames stretch but all text scales correctly
-the tachymeter and damage gauge stretch
-the lower part of the 'dirt mask' doesn't stretch past a 16:9 rectangle, as can be seen on some of the screenshots I posted: http://www.widescreengamingforum.com/forum/viewtopic.php?t=16796
-the minimap is Vert- (the main map is, too), which is the only real issue.