A stiff and synthetic interfacing will give the kilt an uncomfortable waist that does not breathe very well. It will also be harder to mount. Most "normal" interfacing you buy in your local store are to be ironed to the fabric, and it does not work for a kilt. the hair canvas is unfortunately expensive and somewhat difficult to obtain, but is absolutely the best to use. It is easy to fit, soft yet strong enough to hold back the stretch in the kilt fabric.