I've been to MM as a size 24 and did not have any problems with any of the coaster. But that was before X was opened. I rode it as a size 16 and still felt nervous. The way the harnesses are were new to me and at points in the ride you are litterally hanging face down looking at the ground. You have shoulder harnesses that you slip your arms though, then squeze the harness together to lock it. Kind of like putting on a vest. There are multiple ranges of when the harness locks, so I don't think it would be a problem. I would just be nervous if it didn't close very much. Weird, since I am a roller coast junkie, but X just about did me in. It's one wild ride.