Cloudy, first off, if your saddle is pinching your horse's withers then it does NOT fit - not at all. The fact that your horse does not react to it is a tribute to your horse but I would stop riding until I got a saddle that fit. A tight saddle can cause all kinds of problems. Some of the problems you will see right away such as balking in the transitions or even bucking. Some take a little longer to appear and a lot longer to correct such as fistulas.
I found a site that carries a wide variety of Aussie saddles: http://austrailansaddles.com/?gclid=...FQIyxwodyzo6cA
when I tried Australian some years ago I had the Syd Hill and loved it.
BTW, in a Western saddle you may want to try turning your stirrups like the way I posted in this thread (look at my post which is the 3rd one down on page 2) http://www.horseforum.com/viewtopic....11756&start=15