My husband is a bigger guy, though a big smaller in height and weight, and the subs aren't extreme amounts of fun for him. He gets uncomfortable b/c the seats are average-bottom width, and fold down, so if you are wider you're going to take over space on other peoples' seats.
I've heard that it's good to request that you're last on, so that you are in a seat with only one neighbor, rather than squished between two.
The other issue will be his height, because even I (5'3") have to lean down a bit to see through the window, so he might have to contort himself to figure out the best way to get a view through his window.
He should try, at least, IMO.
If all else fails, though, there's a viewing room for those who can't get on the subs (claustrophobic, in a wheelchair, bad knees, etc etc), so just ask the CM to be directed to that area! you see the same things; it's just more obvious that it's a "movie"...