I have never used anything but Flaps 14 for takeoff.
Tpo be honest, I don't think you're supposed to use more than Flaps 14 for take off. If you look at the ‘707 Captain’ FLIGHT MANUAL Part III – Normal Procedures (csx707_manual3.pdf), there is no mention of using more than 14^o of flaps for take off:


TAXI-OUT PROCEDURE
....
Flaps                                                                 EXTEND
      Check LE FLAPS lights illuminate and both outboard and inboard flap position indicators indicate 14.
....

and

AMPLIFIED BEFORE TAKEOFF CHECKLIST
....
Flaps                  14, 14, GREEN LIGHTS            С
     Check both flap position indicators indicate 14 and green LE FLAP lights illuminated.
....