Here's some pics of a articulating spring/hydraulic seat design that might help ease the back pain in rough conditions. There's a little rust from some salt water trials on the seat pan and springs, but you'll get the idea. The side panels are fashioned after those used on some GN boats. The sides are designed to allow bolsters to be build up to keep your hips on the seat. The articulating motion allows the seat pan and back rest to move up and down together, absorbing the bumps so your foot stays on the gas pedal in rough water. With the exception of the side panels, the rest of the seat would be entirely upolstered, covering all the moving parts. The springs are specially wound piano steel wire, the frame is chrome molly steel tube, and the sides are 6061 aluminum. Seat travel is about 4". Food for thought. Enjoy!