Crazy idea: Consider using a larger then required fan and increasing the volume of air. This additional air may result in greater heat absorption from the engine and radiator. It will give a slightly higher velocity at the tail end of the boom, which will help with thrust and yaw. This additional thrust, or reduction in parasitic drag, below the disks may reduce the negative pitching in forward flight slightly. In other words, the loss in efficiency by driving the fan faster than normal may be made up for by other advantages. Forward flight will also unload the fan slightly.

The incoming air is to come from two 'scoops' which are located just below the secondary reductions on both sides of the pilots head. Additional air will come from the top, just aft of the two rotorheads. This air would flow past the engine, through the fan, through a radiator (if the engine is water-cooled), and then down the boom. At the end of the boom, it will be exit straight back or be redirected to either side by the rudder extension. The volume of air is to be greater that that which is required just for cooling. Dduring fast forward flight the airflow entering and exiting the 'engine compartment' will reduce the power consumed by the fan.

Crazy idea 2: Consider having a tube at the center bottom of the cockpit that runs from the nose, between the feet and under the seat to the area of the engine.

This tube will;

The radiator for the 912 must have 78 sq-in of surface area. This is 8" * 10" or 10" diameter. Consider making width greater than height and passing exhaust underneath.