Parallelogram seatposts are much preferred to inline suspension posts. The most popular seatpost seems to be the
Thudbuster, it seems to come with options to suit a range of rider weights. I used to have a Tamer parallelogram suspension post on the Sanatana which could had a spring which was adjusted to suit heavier or lighter riders. I can't remember the model though.
Most stokers enjoy the comfort of a suspension post, especially if they don't do a lot of riding. You do feel the bumps a lot harder on the back, as you don't know when to expect them. The seatposts don't generally take out all of the bumps and vibration, but just deal with the worst of them. It's generally appreciated if the captain can call any bumps anyway, just to be safe.
Emma