Trilogy Verago tree width

I have a young horse. His western saddle is semi-QH bars so I’m thinking he would need a medium tree. He wears a shim pad with his western saddle but doesn’t need blocks to adjust the fit. However, he’s young so I’m worried about his size/shape changing as he puts on muscle or whatever. I LOVE the trilogy Verago for dressage but it doesn’t look like they have adjustable trees and those saddles are a big investment even when purchased used. WWYD?

I love my Verago, but it’s now one size too small for my horse. I am waiting another year to see how she develops before deciding what to do with it (I also have a different Trilogy that is wider that I’m using now). I just wanted to add that they will adjust the tree one size, one time. So, that gives you a little room for change.