"Cotton twill" as in the material Freedom Kilts make's his kilts out of, only in tartan? (and UK's too )

If so, I never realized there was such an animal.

I imagine it would behave similar to any other cotton kilt (barring the cotton flannel at sport kilts).

You should get with Riverkilt (Ron) and get the 411 on his Super Dooper Handy Dandy Iron less kilt Ironing Hangers. He reports he never has to iron after washing by using them. Some assembly required but not difficult or expensive. They use gravity to tension the pleat into shape.