At Lecom-B you switch PBL group members each semester i.e. you will have 4 different groups of 8 during your first two years. You will have from 2 (the 1st semester) to 4 PBL tests each semester. The tests will cover anywhere from 25 to 55 chapters of material in your textbooks. To me, they were actually harder than COMLEX and very, very similar. You will switch facilitators during the middle of each semester i.e. you will have a total of 8 facilitators in your first two years. You may actually get the same one twice. It is not always the case, but basic science professors tended to facilitate more of the first year students and clinicians more of the seciond year groups when my class went through it.
Groups are typically re-divided each semester so that you have students from all quartiles. There will be some from the top of the class, the middle and the lower. They tend to be half male and half female as well. You may occassionally have some groups of 7 depending on how many students there are total in your class.
They try to set it up so that all interviewees get to see a real PBL session... unless the PBL'ers are not available due to a test or break. Sometimes they can set up a "mock" session with volunteers if no real sessions are available. They didn't do this when I interviewed years ago. I think it started during my second year.
Hope I covered the basics for you. I'm getting foggy. It's 4am here and I have 9 more hours left in a 30-hour shift