The best way I ever heard it put was something like "finding comfort in a kayak is like finding comfort on a bicycle; it isn't always easy, and sometimes takes endless adjustments to get it right".
Gerald brings up the sticking point, whereas you kind of need two different seats, actually: one for the "moder" (
), and one for the setter. When you're paddling, good posture is the surest bet for my money. Notice marathon racers and expedition canoeists very seldom use any back support at all. The leaned-back paddling posture so many "recreational" paddlers exhibit looks like an impending sciatica episode to me, and an terribly inefficient way to go about it at best. I'm a big believer in sitting up straight, or even pitched a little forward, and forget the back band. I not only quit installing back bands in my boats, but have actually gone back and removed the ones I had in others to make 'em more comfy. I found them to be deceptive, and leading me away from comfort instead of towards it in a sort of vicious circle. But that's just me.
You'll have to try and manage somehow to get along without me when it comes to sitting in a boat for long stretches though, I simply do not do that. If I'm not paddling, it's never long before I hop out to fish, wade, explore, whatever. And I never like Laz-Z-Boys, either in living rooms or in boats, but that's just me (and my 50-year-old back that never gives me any trouble).