This is not a matter of the dance, but rather the construction of the kilt. Trust me on THIS ONE...

I've made kilts for set dancing and they're NOT the standard casual kilts that we know. These are VERY much like the authentic kilts... but the fell stitching runs to the bottom of the bum. That way, the sway and flair stops at the stitch. It's like having an ACE bandage around the "goods" and pleats hanging from there.

If you look closely at an authentic traditional, the pleats will sway all over the place, up to the fell stitching. At that point, the garment is so tight that it fits snuggly to the body.

My set dancing kilts have the "hip stitching" go the the point where the lift won't reveal "your religion". The kilt pins are also quite heavy to keep the apron from saluting the Queen.