I spent three days on the Greenbrier River, WV, with my new Surf to Summit GTS Expedition kayak seat. It is worth every dime I spent on it. I didn't have any back problems at all. The extra height made all the difference, it really supports your entire back.
Great adjustments, drains water well, good quality. The only CON is the center seat pad is too firm and raised a little higher than the sides. So my tailbone was a little sore by the third day. A gel pad in the center would be perfect.
Over all, this seat out performs all others I've tried by far.