A two+ hour drive would really take it out of me. I would often have to stop and have a 10 minute nap.
I’ve found meds have really helped, I still feel tired, but I don’t have to sleep afterwards or take naps.
Same with riding motorbike, but double. I think it’s the intense concentration for long periods of time.
Have you fiddled with the lumbar support? Also make sure the seat bottom is angled to match the angle of your legs roughly so your weight is (mostly) spread across your butt + legs and not just the back of your butt.
Good tips, thanks! will try that next time