NOTE: The below links for for general saddle fitting, not at all related to Ghost Saddle fitting. Treeless saddles require a different approach as very little can be determined regarding fit by sitting the saddle on the horse. They don't weigh enough to form to the horse without rider weight so both fit and balance must be determined with the rider in place. Please look at the saddle fitting pages under the Ghost Saddles link for information on fitting your Ghost saddle.
My husband and I focused on saddlefitting for several years with the business name Kinetic Equine Analysis - the study of the horse in motion. It doesn't do any good to fit a saddle to the horse standing square - no part of riding involves that except "Salute at X." Not all horses have dramatic changes to their shape when moving, but many do. The links below are part of what I discussed in saddle fitting sessions when that was previously my main focus.
Saddle fitting should not only be focused on the horse as it stands square in your barn. You don’t just sit on your horse and call it a day. You get on and ride. That may be dressage work, jumping, trail or a number of things that you and your partner do together. The underlying theme of all these activities is that your horse is MOVING.
If saddle fitting doesn't relate to the moving horse, you’ve gone little further than fitting a saddle stand. Each point below will be related to the moving horse and how you can test each item.
Even when I happened to be representing a saddle line, I didn’t come to a fitting armed with a saddle, determined to sell it to my audience. My real goal was to look at how your current saddle fit you and your horse. Sometimes we made a very quick fix such as better saddle placement or adding a crupper. Not everyone's style and amount of riding warrants running out and spending $3-5000 on a new saddle if you can find a sufficient solution. There are pads that can help. Sometimes another brand will work or you can look at used saddles available in your area. Hopefully the discussion below will help you check fit on your own before comitting to buying a saddle.