As I've said before, I've had issues with stiffness. All the solutions here are not really ideal.
When I buy a kilt I like to wear it right away, I don't have the patience of Job (or Hamish).

Surely there must be a better material to make the kilts out of? one that will provide the toughness and flexibility that kilts need.

I'm a recent convert to plain workman style kilts, but the problems of the fabric does tend to dissappoint.