Thanks gentlemen. Many moons ago when I was a flight instructor I tossed out questions just to get students to remember that every airplane is a compromise. I have asked many people over the years and only one told me a story very close to the Capt. Air Prox reply. I have no factual evidence but I was told that originally the engines were mounted with the descending prop blades on the inside. There was buffeting of the tail surfaces. One engineer suggested switching the engines from one side to the other. And that was that.