You have me a little bit confused about what you mean by a cuff. I understand a cuff as a downward rounding of the bottom leading edge of the wing to increase the lifting charicteristics of the wing.
Are you refering to possibly the Kreuger flaps on the leading edge that droop down when the aircraft is shut down? or are you possibly refering to the fence on the upper leading edge of the wing. I don't know the specific reason for it on the 727 but a fence is instaled so that air is prevented from flowing parel to the leading edge of the wing rather then over it at high speeds. If I remember right is is located about where the inboard aileron is on the trailing edge. So it might be there to direct airflow over that control surface. But this is just a guess.
Did I hit on what you are looking at or can you narrow down the choices a little bit? I hope this helps.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.