We were there in 2018. In Sept and it was still packed! We used a rental car to get around in the park. I did not see a lot of space available for a class B van let alone any size class C in the more popular attractions parking lots. Even with a smaller class C it will be tough. Only if I were first in line to get in, would i consider the class C. Upon our departure, we did take our class C (31ft) thru the park to go south to Grand Teton NP, and it was no problem because we weren't stopping anywhere and just driving thru