I have a second camera in my scene that I want to match the main camera FOV. 

Vuforia sets the AR Camera FOV at runtime, so I need to update the second camera to match it once Vuforia changes it. The following code does not work:

void Start()

    {

        mainCamera = Camera.main;

        var vuforia = VuforiaARController.Instance;

        vuforia.RegisterVuforiaStartedCallback( OnVuforiaStarted );

    }

    private void OnVuforiaStarted()

    {

        if ( mainCamera != null )

        {

            GetComponentInChildren<Camera>().fieldOfView = mainCamera.fieldOfView;

        }

    }

(Code formatting not working)

If I wait a few additional frames, the mainCamera.fieldOfView does change to match my hardware. Is there any sort of callback/event I can listen to that gets fired when the FOV changes? 

Thanks!