Unless your walking horses are very young you will want at least a 31 cm tree; all of mine are 32 except for the flex trees which are narrower anyway and will not fit a horse that needs a 32 cm tree. Since you are looking at used, see if you can put up a "deposit" and check out the saddle to try on your horse. Just guessing, but I would think the Stubben 31 cm will probably do; be sure to use a clean pad. Even tho a saddle is used, if you return it, you will want to return it in the same condition as when you "borrowed" it. Happy shopping.

ps

Hi, I called Bobby Beech at NB and talked to him this afternoon. I keep getting more and more information and did find out that the Stubben 32 cm is the same as the Tennessean width. The Tennessean is too wide for my horses and I just sold mine so the 31cm should work. I thought this was really good to know and also got my question answered. I can buy a used one for a real good price otherwise I have to order and wait to have them make the saddle if I need a 30 cm. I'm going to do a wither tracing to get a real good idea of what I need. He also said this saddle is being sold alot! That a lot of horses are being bred high in the croup and this also is better for them. My horses are narrow and one is 14.3. I'm short so I don't need a big horse but their harder to fit. The one thing about riding a lot of horses for other people is I KNOW I'M NOT THE ONLY ONE. I hardly ever run into the big 4 cornered Walkers but I may finally have a good show saddle that doesn't sit on their spine like a saddleseat saddle does. Thanks!