The wide-body fuselages have what is known as a larger flat-plate area when the aircraft is viewed head on. Fuselage shapes may be very streamlined, but you will never have true laminar flow from the tip of the spinner to the tail wheel. Around the edges of the fuselage where this airflow begins to separate you begin to build up drag. The larger in diameter this area of separation, the more Flat-plate drag area. Plus Propeller area works in much the same fashion. In a down line, a 17" propeller(when being "back-driven" by the relative wind) has a larger disk area than a 15" diameter propeller. The larger the disk area, the greater the drag when at Idle in a down line. Plus four strokes maintain a slower RPM in a down line, and 2 strokes are revved up by relative wind. JB