Thanks, I love the Cantigas too.  And you're right about the extra fret coming in handy.

I just love the Cantigas de Sta Maria. Thank you for posting this, it's so evocative.

I find that when playing medieval/early music, one would think that because it's so drone-based that one would not need any extra frets, and a purely diatonic fretboard would be just the ticket. However, there are so often edgy 'accidental' notes in this type of music, so I am grateful sometimes to have an extra fret or two even in the minor sounding modes.