Someone in the forum is a member of a 79th re-enactment group. So maybe they will chime in. But as I recall (this has come up before) the kilts were only worn for parade. The kilts were not part of the field uniform. During battle, regular trousers would have been worn. Not sure about the tartan trews. Maybe those were worn by officers. But re-enactors usually potray those units as they were in the field and not on parade.