I'm surprised no ones said it yet. Even if you put a script in one class .cfg, it will "leak" to the rest if you don't write up counterbinds for each of the other class .cfg's.
So for that crouch jump script you would have to rebind jump and duck keys just to ensure nothing leaks:
bind "space" "+jump"
bind "CTRL" "+duck"Put that in every other class's .cfg's and you should be set.