There is a wonderful site at www.wdwig.com/ridsiz.htm
called "Walt Disney World at Large that gives all the information you could ever want about the sizes of seats in the rides, what type seats, how tight are the bars (if any), the turnstiles, etc at the parks. It evan has photos available of lots of rides. There are lots of comments from very large people which are helpful.
When you are done with that part, click on "Home" and get the most information in one place regarding Everthing at WDW. As I read it, I made useful notes, even though when I go in May, it will be my 4th time. I haven't been since they started the FastPass stuff, and read all about that and much more.