From a USAF flight manual.
The cooling flaps are controlled by a switch having the following positions. MID POSITION, OPEN, CLOSE and spring loaded to an unmarked OFF position. When placed in the MID position the flaps open two inches and remain in that position until either OPEN or CLOSE is selected.
The line up check list requires the cooling flaps to be set to the "MID POSITION". This position provides sufficient cooling in hot summer temperatures.
On one occasion an airline in Oz had a engine failure following take off and the crew had to close the flaps on the good engine to reduce drag and be able to remain airborne for a quick circuit and landing. Cooked the engine, but it did the job of which it was asked.