I am a big guy, 6 ft. 250 lb. and the 350Z's seats are very comfortable to me however the thing that really gets me on several hours of driving it is my gas pedal foot that will really start bothering me but the rest of my body is perfectly fine i dont get it on the 280Z because my legs are straiter i think the seet is much higher in the 350Z compared to 280Z.

 

I have 2 herniated discs and the Z doesn't bother my back at all, when I drive my 4runner it kills.