I used to use a pad made for my Aussie until I met a guy at an Expo in Ocala Fl. Who builds Aussie saddles. (I love the way Aussie's talk), it was interesting listening to him. He said the leather flaps are designed to have contact with the horse and to use a regular barrel or western round skirt pad with one.
I was disappointed since I'd spent $60.00 on that Aussie pad and now he says it's not the right pad to use! So, I'm using a Skito pad that's made for a round skirt saddle. Still have the Aussie pad though.