Great pictures!

The narrow fuselage on my Wind S Pro also works well with the Contra.

Based on my experience with my Wind S Pro, my thinking is that a narrow fuselage allows the rudder fin to be more effective, whereas a large profile fuselage masks the rudder fin. which reduces it's effectiveness, and using a Contra Drive shows this effect up because straightening the airflow over the fuselage makes the the fuselage more effective as a lifting surface, which compensates for reduced side area. The net result is more lift from the fuselage, more yaw stability from the rudder fin, and reduced parasitic drag, which is no longer needed for controlling speed on downlines because of the increased braking that you get from the Contra.

Brenner ...