I teach in a district where half of the schools are teaching on a 4X4 block schedule, and the AP courses (all of them) are retained for the full 180-day school year, with the 90-minute class period. Students are scheduled into a "research" class for the second term (semester).
This has created some minor stirrings about "equity", as our students have more contact time prior to the AP exam, but you're never going to achieve true equity.
I can forward a copy of our master schedule later this week or early next (the ink isn't quite dry yet . . .)
Hope this helps!
J. Glenn Mathematics Department Head Paul R. Wharton High School Tampa, FL