Sid,
There are a lot of different treeless saddles out there, aussie, dressage, western and endurance. I don't know of any jump saddles in that category, tho.
You know that a typical saddle is built of leather and wool padding stitched and stretched over a wood (or synthetic) "tree". This tree forms the basis for how the saddle distributes the weight of the rider onto the horse's back without putting the weight directly onto the spine. The tree forms a kind of "bridge" over the spine with a channel down the middle that keeps all weight off the spine. Since the tree is usually fixed in shape, it can fit the back when the horse stands one way, but not fit them when the start moving.
Thus the treeless saddle has flexibility built in because it has not rigid "skeleton". It distribulte the weight but use of padding and attempts to keep the rider's weight off the spine by judicious use of padding.
The advantage , folks say, is the flexibility of the saddle and it's ability to not push hard in some spots like a rigid tree saddle will. The disadvantage is that it may not do as good a job of keeping weight off that spine.
I have heard many people say their horse goes really well treeless and in cases of really broad horses, it might be the only option for a saddle. Other cases I have heard of the horse does well at first but after a month or two develops real soreness.
Treeless saddles take alittle getting used to for the rider. You will be riding more like bareback so may not feel as secure but it might do wonders for developoing a balanced seat.
