The closing limit for the 11:00 section is a little smaller than the number of seats in the classroom, so you should be able to attend the later section. If, however, too many people decide to sleep late, then we may run out of seats. If that happens, then the 9:30 students will need to attend the 9:30 section... the legal 11:00 students can't be expected to sit on the floor.
Two of our three exams are scheduled for the Mod Lab. The 9:30 students must attend the 9:30 exams since the number of computers in the lab is limited.