A true traditional kilt, especially the military kilt, with the 'rise' above the waist, should be worn almost as tightly strapped as a corset. That way your kilt is going nowhere.

Probably because of having learned that at an early age, I have almost always worn all my kilts tightly at the waist, and I invariably wear a wide belt, even with my modern hipster-style kilts. I do not think I have ever come close to having a kilt slip, or feel like it was about to!