Are the seats in the SC the same as the LS? My mother has a 95 SC400 and I never really noticed a problem in all the years she had it. That was until I had to drive it for an extended period of time. Last February I had to drive her to Virginia from here in central Florida. I'd say about the time I got to Daytona Beach on 95 I was started to notice something was not quite right. By the time I reached Jacksonville I was downright uncomfortable. Everything I tried, shifting to the left, the right, hunching over, laying the seat back as far as it would go, nothing helped. By the time I got to NC 7 hours later, my back was hurting bad. I'd have to pull over at rest stop after rest stop and lay down on a bench for a few minutes.
It was a huge relief to finally get to our destination. Unfortunately I could barely sleep on a bed, I had to lay on the floor. For three days I could hardly walk. I left her up there and came back, dreading the return trip when I went back to get her in March I made it, but same thing. My back was wrecked for days after I returned.
Now, I have made this trip quite a few times and never had a seat bother me. In July I rented a car to go pick up my new truck in NY. About 1800 miles up there and 1500 back in an F350 with a vinyl 40/20/40 bench seat and it never bothered me.
Now whenever I drive her car, I can start to feel the discomfort coming on within 10 miles. I told her if I ever have to do that trip again, I am going to tow the car up there Either that or she is going to have to buy me a different seat or milk crate or something to sit on. :D These seats aren't made for everyone, that's for sure.