I am trying an older Jeffries for my 4.5yo, and I'm pretty sure it will fit him in the tree (have to wait to fly back home to check). It needs some flocking adjustment if the tree fits, but should work well for him.
However, I know he is still going to grow and change. He has not much topline from having most of the summer off. And he's still pretty narrow in the shoulders too.
Does anyone know if the trees on these saddles can be adjusted a bit by a saddler? It's not terribly old, as it does have padded flaps, but almost no knee roll (think pencil roll like a Kieffer Wein), and is brown. It does have long billets too, though they could have been added later.