I ride in a Bob Marshall Sport Saddle. I LOVE it, it has COUNTLESS miles on it. I bought it used about 15 years ago, and it was very used then!
I have ridden every kind of horse with it, and the only fit issue is it has kind of low wither clearance. You can get them "peaked" for higher withers, but mine is not.
I use either a Skito pad, or an Equipedic. I prefer the Skito, and HATE the Equipedic.
The only other thing I don't like is that I cannot remount on the trail from the ground. Truth is, I cannot remount from the ground with a treed saddle either,(anymore....), but that's my story, and I'm stickin' to it!!
I just recently had the stirrup leathers replaced, as I had the old Sportack (see, they have been out of business HOW long??) biothane ones with the cam locks, and they had gotten worn, and were not gripping. Had my Mennonite guy make me some out of leather with nylon backing and regular buckles. Boy do they feel secure!!
I am NOT a lightweight rider, and never had any back problems on horses. I finished a 75 with it, but never did a 100.