I made a build of my app using Unity 5.1 and the native VR integration to use with DK2. When I run it on my computer with runtime 0.6.0.1 and my Rift in Direct mode, I see the app mirrored to my primary monitor in a non-stereoscopic view with VRSettings.showDeviceView (awesome function, BTW).
However, I sent my build to some other people and a few of them report that the mirrored image on their primary monitor is windowed and very small (somewhere in the ballpark of 400 pixels wide) instead of fullscreen. I can't find any resolution/fullscreen settings in VRSettings or the rest of the VR namespace; how can I make sure this mirrored display is always in fullscreen and at the native resolution of the primary monitor?
The mirror window's resolution is controlled just like any other app's. If you build your app with the resolution dialog enabled, you can choose whatever resolution or full-screen state you want. If you upgraded from an earlier version of our Unity integration, your project may be set to hide the resolution selector by default. You can make it appear by pressing ALT immediately after launching. After you configure the settings, they should stick on subsequent runs.