Is yours a modified version or standard from the plans. I have one that was scratch built for me, and the tail surfaces we enlarged by about 10%.

It wont flat spin as easily or as neatly as a 3-D plane, but its not bad. Knife edge is allright, but you need a prop with good thrust, I am using a 15x4W APC on mine, MVVS .91 engine with tuned pipe.

Inverted is smooth and stable.