You write:" I'm a heavyweight and the thoughts of all those
treeless saddles make me shiver. This is not going to be an easy
search".
I also ride heavyweight and I delayed and debated about trying a
treeless saddle. Well, I finally did and I really like it. I think the caveat
is, that you have to be a good rider who is well balanced and not a 'butt
sitter'. Your weight has to distributed between your stirrups, thighs and seat.
It also can be pretty wide (especially on a wide horse) because there is no tree
and no 'twist'. Also, getting a proper pad is really important and Skito makes a
great pad just for treeless saddles.
My plan was to buy a used one and if I liked it I would sell it (SS
keep their value real well) and buy one with the features that I wanted. I ended
up liking the original one so much I never bought a new saddle.
