CameraSortModeSetter.cs

// attach this to a camera. It sets the sort mode so 2D object are rendered correctly with a perspective camera.
public class CameraSortModeSetter : MonoBehaviour
{
    void Update()
    {
        if (camera != null && camera.transparencySortMode != TransparencySortMode.Orthographic)
            camera.transparencySortMode = TransparencySortMode.Orthographic;
    }
}

// atach this to child cameras in the camera stack. 
public class CameraSettingSynch : MonoBehaviour
{
    private Camera parentCamera;
    private Camera myCamera;

  // Use this for initialization
	void Start ()
	{
	    parentCamera = transform.parent.gameObject.camera;
	    myCamera = camera; // faster if we store this off..
	}
	
	// Update is called once per frame
	void Update ()
	{
	    myCamera.fov = parentCamera.fov;
	}
}