My name is Simon Shaw the Mumbojumbo guitar technician .I will only discuss my work. The neck of the accoustic guitar is set to have a relief of about twelve thousands of an inch .That is 0.012 ins . i spend about Three to six hours setting it up .The string action or height of strings is created firstly by setting the neck to the above tolerance .Secondly you file down at the bottom of the saddle with sandpaper to create a string height of 5/64 ins on the fat E string measured over the twelvth fret with capo on first fret.4/64 ins over the thin E string and all the other strings lined up so that the string height falls gradually down from fat to thin.Then you measure the height of the strings at the first fret. then you must file the nut at an angle with special files to create the height of string at the nut measured over the first fret.Fat E string 2/64 ins gradually decreasing height to 1/64 ins over first fret at thin e string. But you must first level frets and the recrown .the guitar will play well and sound good . It takes one mistake and you can end up carving a new saddles or Nut from bone blanks .so mistake free and steady is the criticall part .simon shaw