In an unhemmed kilt the weight of the cloth is equally distributed along the length from selvedge to fell. Whereas, a kilt that has been hemmed has a higher weight at the lower end. I have been assured by a Scottish engineer that because there is this extra weight at the end of the 'moment arm', the pendulum effect will cause the kilt to swish more.

Whether, this is true or not, I have no idea. Likewise, how it would be measured is also beyond me.

Regards

Chas