Last year it became almost unbearable to paddle the Perception Tribe 11.5 I have, and I’ve finally fixed that.
I bought a Therm-A-Rest Lite seat cushion:
and glued two strips of loop velcro to the bottom of it. I removed the factory seat from the boat–its thin foam had gone flat–and then glued patches of hook velcro to the plastic. I used Lexel for the adhesive. When gluing the velcro to the seat cushion, I did one strip at a time. I used plenty of adhesive, positioned a strip, put a sheet of waxed paper over it, then opened the valve and stacked a pile of encyclopedias on it.
I finished this a couple weeks ago, but the weather kept me from getting out to test it.
Finally today I took it out for a trial, and it is wonderfully comfortable; I don’t think anything I could do would have worked better.
This cushion feels high and unstable fully inflated; you can finesse the valve enough to let a little air out until it’s supportive and kind of wraps around you.