I see where you're going with that. I have a gray waistcoat that I can turn up the bottum an inch and a half or so all the way around, and it would work fine with a kilt. Put a safetypin on either side and it's good to go. It just happens to be the right shape and length to do that. I need the waistcoat more for my suits, so I can't hem it.

That is a five button waistcoat; I don't know about the evening waistcoats.