That's strange because I have the Funtana X 50 with a YS .63 in it and I didn't have any of those problems. Plane balanced first time and flies like a dream. It will knife edge all day long. Maybe you got a bad one. Never owned a Fliton plane. Here's a short video we shot of the plane.

http://media.putfile.com/Funtana-X-Maiden-Day-Out