First when cutting away the monocote for the elevator and rudder, do not use your hobby knife use a soldering iron. You will not score the balsa this way and take a chance on weakening them. Second seriously consider removing the dihedral in the wings. I have trained 3 people using my Avistar without the dihedral and all of them have thought it was much easier to fly then the Avistar with the dihedral. It will stay in a bank without additional aileron input, not have any adverse yaw, fly inverted easier and roll more axially. This can be easily done by sanding the root rib with a belt sander so the rib is vertical and adding a 2" fiberglass reinforcement when you join the wing. It is much stronger then the stock wing.