how to determine whats the best nut slot height to file on a new nut or when the strings seem to be sitting a little too high on the nut? on a fretted bass guitar. all the set up manuals i have seen dont talk about this at all. i've got a 6 string SX ursa jazz bass on which i need to fix the nut slots. so please keep the low B and high C string in mind. also are there special round files for filing nut slots, each of varying thickness for different strings as the gauges go from .130 to .040?