Eyefinity / Surround Specific Solution
Same .ini+hex method as widescreen
1) Resolution
Documents\Deus Ex - Invisible War\user.ini
FullscreenViewportY=1050
FullscreenViewportX=5040
2) FOV
Program Files\Deus Ex Invisible War\System\Engine.d2u
Replace all 3 instances of 00 00 AA 42 with 00 00 9A 43 (equivalent to decimal FOV 308)
3) UI
Program Files\Deus Ex Invisible War\System\Default.ini
fov__d=21 (scale of the "wheel" interface)
AssumedUIScreenWidth__d=1680 (your single-screen width)
AssumedUIScreenHeight__d=480 (default height)
Some strange camera angles result.
You can fix some of these by editing the [ConversationCamera] settings in Default.ini. I don't know exactly how, but dividing all Angle and Dist values by two is much better already.
Code:
[ConversationCamera]
SlightAngle=7.5
AboveAngle=30.0
ShoulderAngle=7.5
ShoulderMult=0.7
HeadMult=0.25
FaceScalar=0.38
SideTightDist=1.0
SideMidDist=1.5
SideAboveDist=1.0
SideAbove45Dist=1.0
ShouldersLeftDist=1.0
ShouldersRightDist=1.0
HeadTightDist=1.2
HeadMidDist=2.75
HeadLeftDist=1.2
HeadRightDist=1.2
HeadSlightLeftDist=1.2
HeadSlightRightDist=1.2
StraightAboveDist=1.16