The usual placement is forward of, or near the front of the motor and the same in the cockpit, relative to the driver. At one time some of the funny car teams were attaching a nozzle to a length of braided line and putting it inside the diaper as that was quite often the root of the fire source. On a blown car with 20lbs of agent I usually put one engine bay nozzle low (for an oil pan fire) and one at the base of the blower. With two cockpit nozzles I aim one at the driver's legs and the other at his torso.
Roo