AR glasses, unity app renders left image on both L/R screens

I have a pair of AR glasses. I want stereoscopic 3D without using Vuforia.

I want to set up two cameras where camera left is rendered on screen left and right cam on right screen.

But it fails.

Default is that screen is cloned, same images shows in both screens.

But when screen is extended it will behave like one big screen of 2560x720

In an ordinary Android app one get left/right correct. One get one image in left screen and another in the right one. If one look at screenshot with Android Device Monitor you get 2560x720 and two images side by side

When one extends window in Unity3D app Unity puts the left image and render it on both screens! If one calls Screen.currentResolution.ToString() in Unity script it gives 2560x720. If one has two cameras, camera left with viewport rect x=0 w=0.5 and right camera with x=0.5 x=0.5 then only left camera renders but on both screens. If one look at screenshot with Android Device Monitor you get 2560x720 but the right part x>1280 is black/no image

When running the same Unity app but without extending the display. Then Screen.currentResolution.ToString() in Unity script will give 1280x720. If one has two cameras, camera left with viewport rect x=0 w=0.5 and right camera with x=0.5 x=0.5 then both cameras will be rendered side by side on both screens. Cloned....

Thus it works in android app but not in Unity3d. What can be done? What is Vuforia doing?

Running Unity 5.3.4.f1

Unity editor running on PC Windows10 64

Target device running Android 4.4

Thanks!

Kristofer