They should helpful in a small way and I dont know of any reason why you shouldnt take them....
Ill look into it a little more for you and post back if I turn up something relevant.
Edit: id like to change that advice and advise you NOT to use either of those substances during benzo WD.
Your right that they have some anti-convulsant properties but they also increase cell excitability and can cause anxiety (something you will get alot of during WD).
Im not saying it would be dangerous but it has the potential to be really uncomfortable.