I am a recently retired airline pilot and as a boy in the early sixties I finagaled a ride in the back seat of the old un-modified Navion. As you said the plane was as smooth as a 55 Caddy and I did notice the performance with the older less-powerful engine was not exactly stellar!! I have always loved the Navion especially the upgraded ones with the bubble canopy, tip tanks, and a bigger engine. Thanks, Skip