RE: DOES EVERYONE MAKE THE SAME ASSUMPTION?
To confirm what BocaBen said, I have a Flip 3D with the YS 63 and it is a blast to fly. It's one of the best 3D planes I have owned.
One of my friends has a Flip 3D with an O.S. 50 on it, and it is more of a sport flyer plane in comparison to mine with the YS 63.
In my opinion, the YS 63 is the perfect engine for the Flip 3D. It's nice having the tank on the CG too.
Jim