A deeper back would be helpful at forcing me to stay well postured. I've used a 3" inset for years now. My hips and back are getting very contorted and i'm constantly (like every 45 seconds) trying to reposition myself. I'd love a more supportive back, but when folded, the side bolsters majorly restrict the fold.
The resultant package is VERY difficult to get past the steering wheel in the car! The back canes are ~45* to the seat framing.