This 3.66:1 Speed 280 gear drive was chosen beacause it extends the shaft enough to fit properly through the center of the dummy engine and cowling.  Its also stronger than the typical Horst gearbox and should take the power of the 280BB motor better.

The 4mm prop shaft and Graupner stepped collet type adapter lets me use any prop.   One disadvantage of this arrangement is that the motor is placed further aft which make it more difficult to acheive proper center of gravity.

The little scale air intake snorkel is functional.  It directs ventilation toward the motor to help cooling.