Because I just love the line-pull increase of pushers in the upper loop of the vertical eight, as well as in corners 3 & 4 of the hourglass, (caused by the prop gyro force yawing the nose out in outside loops/corners). As the same force yaws the nose in inside loops/corners, I had to install an inverted functioning Rabe rudder being coupled to the elevator i.e. deflecting to the outside with elevator up, keeping line pull up. This has nothing to do with the in-line arrangement which was chosen to allow easier compensation of landing gear drag by a -1° down incidence of the stabilizer.