One might surmise from the above observation that the low wing on the Piper influences the tail less with flap extension than on the Cessna. If downwash is the single most important factor (or the only important factor), then why would the Pipers pitch down? A reduction in the downwash force on the tail would seem to simply reduce the amount of pitch up (because the downwash effect is only reduced, not eliminated) unless there is another moment opposing it, like an increase in negative pitching moment, which is well known to occur with an increase in camber. Even if the downwash effect on the tail was totally eliminated by the low wing position, the downward pitching of the Pipers is evidence of an increase in the negative pitching moment. Since this is a fundamental and well known force in aerodynamics, why discount it?