Hmmmm.... Unsure myself, I'd suggest asking Mad Texan (I think). He seems to be the man who knows. You'll find him here on the Sierra Arcanum WorldEd Forum.. Just post the same question up on that forum and I'm sure you'll get an answer (either from him or someone else who knows).
Just open the proto file you want to edit in your hex editor. However, you need to know what the offsets are for the values you want to edit... I have some of those scattered about my HD but Otto Krupp of Krupp Gun Works is going to be posting them all on a website soon. When that happens, I'll make sure that link ends up in this post (or on the Sierra forums at least)