still like carrier seat and S40, did 45 miles yesterday along the central CA coast. the bike is great but would be uncomfortable for me without the carrier seat. the seat only comes in medium size so measure carefully. the seat fits the S40 with a little wiggle room, I used the slider bolt for top attachment vs. trimmed top tabs, and used wide velcro so no part of the seat contacts the frame. I had a back and neck injury over thirty years ago, so the wide top of the carrier seat makes me most comfy when pushing up a hill. the carrier has great lumbar support and I don't slip down as I did with the stock seat. also no headrest needed because the seat pushes the sholders foward to a neutral position.