I've found that, if a pleat has any taper at all from the hips to the waist, the pleat tends to want to squidge a bit wider as you sew from the hips to the waist. I always under-pin the size of the pleat at the waist by about 1/32", and they wind up the right size. I then flare a bit toward the top of the kilt, which is essential for a 3" rise.