I have the same coach and at 6'2" 320 pounds, I find the seats pretty comfortable. First off, when I bought the coach, the driver's seat was blocked from going all the way back, by the trim on the FWS. I cut an arc in the trim and the seat now goes all the way back and touches the slide wall. MUCH more leg space!
Second, you have an adjustable lumbar support that needs to be adjusted to you. Your seat not only raises and lowers the seat cushion front to rear, it also raises the cushion up and down. An improperly adjusted height can cause stress on your shoulders because there is too much weight on your forearms while they're leaning on the armrests. Play with the seat height.
The seat bottom adjusts front to back, too much lift in the front can put undo pressure on the underside of your thighs, too low and you're pitched forward. Again, play with the adjustments.
Lastly, for whatever reason, the seatbelt is waaaay to tight and pulls and stresses my shoulder. I bought a seat belt stop on Amazon. It locks the seatbelt so it can only retract so far, taking the stress off of my shoulder. It doesn't effect how the seatbelt works.
Don't forget pedal adjustments too. I use my cruise 90% of the time and move my legs around often. I typically do four hours of driving before I have to pee! With Comfort Drive, I'm very relaxed.
Linear Mode
