The horses HAVE told the story. There are many top level endurance horses out there that have been competing year after year, literally thousands of miles, in treeless saddles, quite successfully. I literally could not even begin to tell you how many treeless riders I have seen on the trails and at endurance rides. It’s not a rare thing. It’s not the ocassional person who decides to try something different. Riding treeless is becoming very common.
It doesn’t take years to make a horse back sore. It generally takes only a few rides. If a saddle is pinching, pressing, and hurting, the horse will start to show signs fairly quick. This will be even more evident in mountainous regions where the horses are going up and down hills. The big name treeless competitors I mentioned earlier live in mountainous regions and ride on very difficult and steep trails.
Spend some time on endurance.net looking at Tevis photo albums. Check out the photos from the vet checks and tell me how many Bob Marshall and Freeform saddles you see. People don’t just willy nilly flounce off to Tevis in a saddle that sores up their horse, or a saddle they haven’t been training regularly in. People who go to Tevis generally have done their homework and have been conditioning for months or even years. I tend to think that most of them (no, not all) know what they’re doing.
You are assuming that all the riders who have ridden treeless for 3 or 6 or 10 years are suddenly out of nowhere going to have every horse in the barn pop up lame and back sore after all those years of treeless. It doesn’t usually work that way. If a saddle is going to cause problems, it shows up sooner rather than later.
And just to clarify, I am NOT saying that treeless is the only way to ride, or that it’s the best. I don’t personally care what a person rides their horse in. As long as the horse and rider are both comfortable, sound, and happy, it doesn’ matter.