Horses with flat backs are shaped like a table top. They usually have low wither definition and a straight top-line, making traditional saddles uncomfortable and the horses hard to fit.
The problem with missing withers is that most saddles are built with normal withers in mind. The withers help keep the saddle in place, creating a ridge.
Important Points to note while saddle fitting a flat-backed horse:
The first thing we'd recommend for a flat-backed horse is a saddle especially designed for your horse's conformation. We have a few options. Many of these are designed for halflingers, which have flat top-lines and shorter backs, but these saddles will also work for mutton-withered horses with normal back lengths. Try out our newest option, the Big Horn Flat Top-Line Saddle. We also frequently recommend the Big Horn Halflinger Cordura Saddle, Big Horn Mutton-Withered Saddle, or if your horse has a wide back, the Big Horn Extra Wide Trail. The trees on these saddles do not depend upon the withers to keep the saddle in place and evenly distribute your weight without putting too much weight in the front or back.
Most, but not all horses with flat backs require a wide tree because of the width of their backs. However, horses with narrow backs can also fall into this category. It's important to know what width your horse requires. Try out our downloadable templates for this.
A straight-back pad will help too. We recommend the model by Reinsman.