I have a nice heavy Dirk Belt and a couple cool-looking Edwardian buckles and a dirk too... however I rarely wear that stuff.

In spite of my "figure" resembling a big potato I've never had any trouble with my kilts staying put.

Dirk Belts were never intended to support the kilt- my theory is that Americans (and others) use the belt for that purpose by false analogy with pants ("pants need a belt to hold them up, so a kilt must be like that too").

Ditto shoving the Dirk Belt through the kilt's loops (if the kilt has them- mine don't).