Designers learned as they went....the "A" model Chinook had a very sharp end to the Aft Pylon and was quite sensitive in Yaw. The subsequent models had a squared off end to the Aft Pylon which provided the equal of about 37 feet more fin or some such number....and was much more stable in Yaw. The A and B models had dual channel three axis SAS systems.
Starting with the "C" model the aircraft were equipped with an additional Pitch SAS system.
The earlier Piasecki CH-21 has no SAS but did have stabilizing fins on the Aft Pylon.
The H-25 or HUP had neighter SAS or Fins..