I'd advise against it. First, the waistcoat should never been tucked into the kilt; it just isn't designed (or intended) to do that. Secondly, when wearing a waistcoat the belt should be dispensed with as it presents an awkward appearance peeping out from under the waistcoat. Thirdly, the belt was/is intended to be worn with a dirk, and in those circumstances would be buckled over the waistcoat (as it is in the illustration on the cover of Thompson's book).

Since the kilt is a fitted garment that does not require a belt to stay in place, why bother with one in the first place?