Sounds fabulous Will, I'd love to see some pictures of that! I assume the un-capoed tuning would be something like FCGDA? You'd need a hell of a string to produce that low F if it's in mandocello tuning. If it's a mandolin on the 7th fret though, does that mean the top four strings are a fifth below a mandolin? (i.e. mandola tuning?) A true mandocello is an octave and a fifth below the mandolin; the same relationship as the cello to the violin.