My WS Tarpon came with an integral backrest and self adhesive pad for the seat. The pad is thin but surprisingly comfortable. Some people don't like the back rest, others love it - for me so far so good. Being fairly rigid its great to lean back against for a rest after a lengthy paddle in the 'forward tilt' position. My legs were asleap when I got back to the landing on Sunday.
Maybe a bit of flexing from time to time which is much easier in a SOT