Following up a Pinterest picture I came across some very interesting looking upright bass variants. Might be something here to inspire one of you.
"The Canotto(Italian for rowboat) upright acoustic bass features full bass sound but uses simplified and historically proven construction techniques. It was also designed to be playable by folks that already know how to play the bass guitar."
Cello sized basses, with frets, only two strings, intended for children, but why should they have all the fun? Note the surprise on the bottom. Interesting head design. More pictures: here, here, and here.
There are plans available on the site for the Libellula, and the Guild of American Luthiers sells plans for the Canotto: plan #50.
Thanks for the links!! Close up on my list of stuff to build and I ordered the Canotto/Savart plans just now.
I LOVE these! If I had a workshop, I'd give one a try.