SteamVR passthrough camera view

I’m trying to implement an AR passthrough mode using the Valve Index stereo cameras to selectively overlay the camera feed on to of the game world. Using the OpenVR IVRTrackedCamera functions I can access the image textures just fine, but I’m not able to get the image projection and frame prediction right. UE4 seems to have an AR module with the same functionality built-in, but it doesn’t seem to have any support for SteamVR, or VR headsets in general.

Had anyone been able to implement this in UE4, or have any other tips?