I bought a set similar to those for my sandrail. I haven't finished the project yet, so I can't speak to long duration butt time. One thing I do know is they sit kind of straight up and down. I'm going to have to build my brackets so that the seat sits very reclined to be comfortable, and with no adjustable back, you get what you get.
If you do decide to do it, I found mine on ebay. They're Hunsaker and came in a pair with the cushioned covers and were about $150 to my door.
