Best practices: hierarchy does not seem possible because redefined method need other private methods

I need to add a single line of code to the method private void FixedUpdate() of the script: Standard Assets > Characters > FirstPersonController > Scripts > RigidbodyFirstPersonController.cs

I think I cannot use hierarchy because that method need other private variables and methods.

What I have done is to copy and paste the whole code in another script. Then, I have added the single line I needed to add. I explained exactly what I did here: http://answers.unity3d.com/questions/1084480/make-camera-tracking-the-view-in-vr.html#answer-1093443

Is it the best way to do it? It does not seem very elegant...