Changing the black pixels outside the fov

Hi, I'm very new to Unity and the Rift. I've been trying to get the black pixels outside the field of view to blink or better yet, show an undistorted quad in the corner that changes color depending on what's happening in the game.

To put a quad in the black area outside the fov, I've tried using culling masks and adding a new camera under the OVRPlayerController and outside the OVRCameraRig so that only the new camera can see the undistorted quad. I've also set the depth of the new camera to be larger than the depth for the cameras in OVRCameraRig. In the preview, I can see the quad but when I go to build the game, nothing from the new camera I added has been included.

For making the black pixels outside the fov blink, I tried alternating between a black and white background color for the camera component that gets added to OVRPlayerController when the game runs. This doesn't work in the build either, but the preview shows the black pixels blinking.

Has anyone been able to successfully alter the black area outside of the field of view or have any tips? Thanks!