Koto designs

I'm planning to make a bowed zither, similar to a koto but with a flat
top instead of an arched top. I thought of making curved bridges at both
ends, designing so that I can bow all 8 strings. Has anyone built, seen
or played such an instrument? If so, any pics or designs? The problem I
foresee is that the two highest strings, being further away from the
soundboard, might lose volume.

Thanks in anticipation.

Kind Regards