I'm buying a horse, and he's pretty narrow, but he's also undermuscled (and he's not quite six, so I'm hoping he'll fill out a little more, too). A friend recommends the Abetta Endurance saddle, and it sounds good, but I'm wondering which tree to get. They don't offer a semi quarter horse tree--just standard, wide (not for me!), and gaited. It sounds like the gaited has a narrower but higher gullet, a more acute angle between the bars (the opposite of a wide tree), and is flared in the shoulder to allow the "action" of gaited horses. My future horse isn't gaited, but he's very narrow and his shoulders will likely muscle up with more work.
What do you guys think? Here are some photos of his back that the seller took for me: