Thanks for the visual, Bob.
Here's the current version of the fretboard. The terminus may not stay square. Not sure.
I'm thinking either ebony or possibly wenge for the fingerboard and recessed turquoise for the markers. Turquoise is not exactly authentic Craftsman but I'm thinking a splash of color might be nice. Maybe Taliesin West
I see my center line did not disappear as expected. Don't have time to fix it at the moment.