Thorowgood saddles are very nice quality and very comfortable too. The are supposed to come in all different sizes, not just for wide horses. The fish system is a good idea too.
However, if your budget is $500, unless you find one used, I tink that they're out of your range. Feel free to correct me if I'm wrong. Thorowgood dressage saddles here cost bout $900CAD.
That being said, if I had the cash, I would be running out to buy one right now.
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