Off center projection matrix does not move skybox

Hello all,

in the Android app I'm currently writing I have two views of the same scene next to each other in landscape mode. I'm using 2 cameras (one for each eye), each using half of the view port. The cameras have an offset to each other to get a real 3D effect. Everything works fine up to this point.

Now I need to take different eye distances into account. For a display of 4" width, the default eye distance is 2". My eye distance for example is more than 2.5". To accomodate for this, I move the center of the view off center of the view port to the outside (or to the inside for a smaller-than-default eye width).

For this, I change the projectionMatrix of the camera like this:

 void moveProjectionMatrix(float _flShiftValue)
 {
     Matrix4x4 m4x4Left = m_m4x4OriginalProjectionLeft;
     m4x4Left.m02 += _flShiftValue;
     m_cameraLeft.projectionMatrix = m4x4Left;
     Matrix4x4 m4x4Right = m_m4x4OriginalProjectionRight;
     m4x4Right.m02 -= _flShiftValue;
     m_cameraRight.projectionMatrix = m4x4Right;
 }

I call moveProjectionMatrix() in Update() and set the global variables

    m_m4x4OriginalProjectionLeft = m_cameraLeft.projectionMatrix;
    m_m4x4OriginalProjectionRight = m_cameraRight.projectionMatrix;

in Start() which works fine. The only problem is, that the skybox is not offset like the cameras. I've read several posts how to fix this, e. g.

http://forum.unity3d.com/threads/152428-Setting-camera-projection-matrix-breaks-shadows-and-skybox http://answers.unity3d.com/questions/17305/Off-centre-projection-matrix-breaks-cascaded-shadows.html

but my mathematical knowledge about matrices etc. isn't good enough to figure out how to fix this.

Any hints would be highly appreciated!

Thanks in advance!

Andreas