A Paint Horse's colour is the famous part; his saddle fitting is decided by the stock-horse frame underneath it. Most Paints are built like the Quarter Horses they are closely related to: muscular shoulders and hindquarters, a strong back that in many individuals slopes slightly downhill from hip to wither, and a round barrel. Fitting checks follow that build: tree width for the shoulder, contact and levelness on a back that may not be level itself, clearance judged on the individual horse's withers, which in this breed vary from defined to barely there, and stability through the jog and lope gaits his saddle will actually be used at.
Tree width and the stock-horse shoulder
Start ungirthed and judge the tree against his shoulders. A medium-wide to wide tree is the usual Paint answer, but the test is contact: the saddle should settle with its seat level relative to the back, its points lying flat against the shoulder rather than digging at their tips, and no daylight showing where the panels should meet the back at the front. A too-narrow tree on a Paint perches above the muscle and pinches as the shoulder moves, which the horse reports by shortening in front.
Levelness on a downhill back
Many stock horses stand slightly higher at the hip than at the wither, which tips a saddle, and its rider, forward. Check the seat's balance from the side on level ground: if the lowest point of the seat falls too far forward, the rider will fight position all ride and the saddle will load the shoulder. Solutions live in panel flocking, shimming designed for the purpose, or a different tree, in that order of preference, not in sitting differently. Check also for bridging along the back, since a straighter saddle on a slightly dipped or downhill back can touch at the ends and float in the middle. Run the hand test girthed, then confirm with the sweat pattern after a working ride.
Wither clearance: judge this horse, not the breed
Paints are inconsistent here, so measure the individual. Some carry clear, well-defined withers needing proper pommel clearance; others are mutton-withered and wide, where clearance is easy but the saddle loses its anchor. Mounted, with the saddle settled into work, you want visible daylight through the gullet along the spine and space over the wither that survives the horse lowering and stretching his neck, since a Paint asked to stretch down can bring his withers up into a saddle that cleared them at the halt.
Stability at the jog and lope
A round barrel and smooth back invite sideways travel, so test in his working gaits. At the jog, the saddle should track centred without the rider constantly re-seating it; at the lope, on both leads and through transitions, watch for roll towards the lead side or a slow creep forward. Have someone watch from behind on a circle each way. Girth or cinch position and type can fine-tune a nearly right saddle, and a well-fitting pad evens minor imperfections, but persistent roll means the tree's shape and the barrel's shape disagree, and no accessory honestly fixes that. After the ride, palpate his back for flinch, heat, or swelling, and check the shoulder for rubs where a migrating saddle has been working.
Write down the stock-horse answer
Tree, rigging or girthing arrangement, and pad, the combination that keeps a Paint centred and comfortable is a set worth recording exactly. KinsLe's Pet Passport keeps your Paint Horse's saddle measurements and fitting notes together with his records in one portable packet, so a replacement saddle or a new fitter starts from the combination already proven on his back.