danamania

If I were discussing the Contra with a twin-engine enthusiast, I would probably mention two examples from general aviation: The Cessna 337 Skymaster twin with the push-pull engines; and the Piper with the counter-rotating props (Seneca perhaps, I forgot which model).  While not identical to the Contra set-up that we have for models, these twin engine configurations demonstrate that there are ways to manage the untoward effects of having two props that involve sharing the same thrust line and contra-rotation.  The twin enthusiast would then have to disprove the engineering know-how that made these two very successful GA configurations work for many years of safe operation in the hands of satisfied customers.  Not sure I could make a cogent argument out of it, but then again, it would be difficult for the other guy to argue against these terrific twin engine aircraft!