You may want to put more of the waist measure into the apron side. Then, even if your hip measure is split 50/50, you will have a taper between bottom of fell and waist.
Won't work. If you tapered the pleats, you'd wind up with the apron measurement at the waist being bigger than the apron measurement at the hips, which would give the apron a reverse taper. Which you don't want.

The only thing you can do here is make a cylindrical kilt.