In case it's any help, Jean-François Dutertre gave these modal tunings for the épinette (assuming one course of melody string(s) [chanterelles] and three drones [bourdons] with his 1974 recording, L'Épinette des Vosges (Le Chant du Monde LDX 74536):

Do [Ionian]:   g - g - C - c

Sol [Mixolydian]:   g - g - G - d

Ré [Dorian]:   g - a - D - d   or, more practically,   f - g - C - c

La [Aeolian]:   g - a - A -e   or, more practically,   f - g - G - d

Mi [Phrygian]:   eflat - g - C - c

I can never remember exactly how the French mode names equate to the ecclesiastical ones, so no guarantees that the above are correctly described; the intervals are right, though.  Those tunings are for the long-scale épinette, so the pitches may, for your purposes, be an octave -or even two- higher than I've indicated.  It's worth experimenting, too; I found several other tunings which were rather good, though it's twenty-odd years ago and I don't recall the details.  I should mention that I always played in the traditional style; that is to say, melody on chanterelles and drones on the bourdons: I almost never used fingered chords, though Dutertre certainly did, to good effect.  A particularly nice effect may be obtained by bouncing a light stick on the strings, a little as you might do with a hammered dulcimer, instead of plucking.

Malcolm