If it is the CG Extra you have you may want to get the templates and plans then build the stock wing for your plane. Not sure what you would think of as poor flying but I have never flown one that wasn't perfect but they have all been stock built or just minor mods. I have never seen one with a foam core wing so I suspect there is the problem or perhaps the incidence or CG? Hard to say. If we were only allowed one plane this would be the one I kept. It's even smoother then the 40% I had and a ton better then the 30% I was flying. You can build the Great Planes Extra kit and make it a bunch lighter, it's another good one.