I'm 6'1 and I fit pretty comfortably. I'm a thin guy though, so the extra bolstering in the seats is definitely welcomed
I haven't had any issues with comfort so far and I have plenty of headroom. I definitely have the seat set all to the back and lowered however.
As far as passengers go, my cousin who's 6'4 sat in there, and I would have to say is probably the max you could go.
I have yet to take a long distance (i.e. more than 1.5hrs) trip, so its hard to say how my body would take the trip. I've only cruised around for about an hour or so, but in that time, I was still comfy, no cramping or squirming around. maybe i should take a random trip this weekend, hahah.