There have been other threads on this topic so you may want to look in the archives for what others have to say. Me personally, I always treat zero frets like Non-zero fret guitars. By that I mean, the height of the zero fret is determined by how high or low you want your 1st fret action to be ( just like a nut, I adjust the height to desired 1st fret action). You also can adjust the zero fret (by filing it)as to where the string(s) comes off the zero fret( that is your scale start point). If you need to sharpen or flatten a string you can file that fret ( to a limited degree) to help achieve your objective. The nut, in this case, is really nothing more than a string guide and should always be filed so that the strings do not come off the nut but rather the zero fret. I don't like "zero" fret guitars because I always adjust my fingerboard scale ( I always install Buzz Feiten sys. on my guitars). So to me a zero fret is just "in the way".
