Camera Depth Shader Breaking on Oculus Rift / Gear VR

I am using a portal style effect using multiple cameras rendering at different depths and using a shader to define where the portals are. It works well but the problem is that is doesn't work with the Oculus OVR cameras. Any help is appreciated!

This is the code I'm working off of: http://algoholic.eu/unity3d-indie-free-portal-effect-project-sources/ Video here: https://www.youtube.com/watch?v=YMZM6umLp3o

Everything renders fine if I delete the OVRManager script. So that means it breaks down somewhere in the process of rendering for the rift.

It looks like OVRManager takes the cameras views, processes them in a buffer and then renders the final output to a texture which is drawn to the screen. So I am thinking that is ignoring the portal shaders.

Any ideas on how I could work with the OVRManager or change the shader to not break on the rift?