Saddle size will depend on HIS SIZE and the model of saddle. He needs to go sit in various makes and models of saddles, to see what is comfortable.
A suggestion for male riders, is to look at flat seated saddles, with a wider twist if possible. My guys here, who ride Western hate my narrow twist saddle, anything with the built-up front on it. They are experienced English riders, comfortable on horses, in charge of their horses for a variety of riding activities, so not in the “beginner or intermediate” rider catagory.
My guys are wearing 34-35" waistband pants, not really big guys, easily fit a 15" seat Western saddle. A guy with larger hips, probably will need a bigger seated saddle.
That high cantle on barrel saddles really DOES HOLD you still. Doesn’t allow much of any movement for comfort adjustments. I would certainly not advise taking one Trail Riding all day, you are pretty locked into position for that time you are riding. I know I move myself around in a saddle over several hours of ridng, would be quite unhappy with that high cantle over a long ride.
Maybe things have changed, but the old cutting horse saddles had very FLAT cantles in the past. Sure were not going to hold/force you in place for the rocket speed of a barrel run and turns.
I would be more likely to look at Roping saddles, though they are heavy. Rider has to stay in position for the quick start out of the box. Steer Roping doesn’t have or need the lower cantle for quick dismount used in Calf Roping and tying the calf FAST.
I expect there are a number of higher cantle saddles, without the really tall ones being the ONLY kind of saddle your son could be happy riding in. If the cantle doesn’t wrap around hips so fat forward, the rider legs have more room to adjust and be comfortable sitting, could take a smaller seat size if person is not a big person. I had one with that cantle that really came around you, hated it, couldn’t move, made my hips sore with no adjustability during a ride.
Back to trying out saddles with actual sitting on them for how they feel.
With all the saddle problems I see, I would never order a saddle without sitting in it, trying it on my horse who is ALSO difficult to fit. Especially just buying it by a seat measurement. A 17" seat size in Western is HUGE. Probably going to put the rider back on the loin area, which can be real hard on the horse. I would expect horse to have a sore back with much use, having a rider sitting back that far.
