I've tried riding in a skirt - used a really long and wide one, and my riding breeches underneath, with an English saddle. My horse is used to cloth waving around his body, so he was cool with that, and I found it rather comfortable and warm in the colder months. :) But I used it mostly just for a couple of photo shoots, as I like dressing light in everyday situations - the less layers, the better I feel.
Interested to see some pictures of you riding in a skirt! :)
I have come a long way, to surrender my shadow to the shadow of my horse.