We are talking about a traditional kilt right? If so it should be at the top of the knees to mid knee at the longest, I prefer wearing kilts to the top of the knee as it gives me the freedom of movement that a longer kilt may not provide. I also think if you are getting a garment made for you, any garment, then said garment should fit correctly, so with a kilt I go get measured for it and that seems to work out fine for me. If I were to wear a standard 24" length I would have to wear it far too high. Do not worry about showing too much leg, and like Archangel says get some shorter boxers.