Thor seat was a game changer for me. Totally fixed the dreaded recumbutt and the seat area has a nice contour to it. Combine that with a thicker Ventisit pad and you have one comfortable ride. I believe I have a 2021 S40 and the Thor seat only required me to drill two holes near the seat area, screwed directly into the existing frame tabs, two small holes mid way up the back to run a zip tie to attach to the frame. The zip tie is hidden and the heavy duty velcro on the frame attaches to the seat and is very secure. It does raise your shoulders up a bit but I'll sacrifice some aerodynamics for comfort.