I am fortunate to have been the Shanghai Disney Resort twice. I think this a great ride...I am 6'1" 230lb and had no problem size wise for the standard vehicle seats. You do indeed need to be able to bend your knees; it's similar to Flight of the Passage but you really are "straddling" a bike and leaning forward.
However, there was at least one train in operation in Shanghai where the back two seats were real "seats" allowing some disabled riders to enjoy the ride in a traditional roller coaster seating situation (and in fact, these looked to be more spacious seats than say Space Mountain at
Disneyland).