Wool and linen in kilts

[HeathBar]

I have seen some kilts use a heavy canvas as the support structure for the kilt. But traditionally a hair canvas is used which contains a mixture of hair and fibers to create the stiffness. I suppose it could contain some linen in its content. Is it just the combination of wool and linen that is forbidden?

Edit:

I have looked at two different hair canvas contents and none mentioned linen. It was usually wool and goat hair, or polyester, wool, cotton, and hair. The hair is usually goat and or horse.