First thing I'd do is add 1/2" to both measurements. You'll put the buckles on at the actual measurements, but the extra half inch gives you a little wiggle room in case your pleats are a hair shy or if you expand a little.

For the splits, I'd go for:

waist: 21 1/2 apron; 20 pleats

hips: 22 1/2 apron; 23 pleats

Second thing is that the length measurement sounds _really_ long. When you add a 2" rise to that for the layout, you'll have a kilt that's 28" long overall. I've never made a kilt that long, even for someone who's over 6'4". I would double-check that length before I did anything else unless you are really, _really_ tall.