RE: Learning the Flatspin
A couple things to try. First this is how I get into one. I go vertical and get plenty high, then cut the power with the plane still pointing up. When it stalls, I give full down, full right rudder and full left aile with the engine at idle. After the first few spins I start to bring the aile back to center as I add a little power. The amount of opposite aile and throttle is different on every plane. You need to find the sweet spot. Some planes need 100% opposite aile and some need centered aile. Same on throttle, some need 1/3 power some need full. I have an Ult that will go flat at idle. So experiment.
Second thing you might try is going into a flat spin from a blender. To do this climb out and point the nose straight down. After the plane gains a little airspeed, give the inputs I described above. This can be a very violent maneuver, so increase the airspeed a little at a time.
Also,like Jezmo said CG is a big part of it. You have your CG perfect for pattern. This does not mean it is right for a flat spin. If you still cant get it flat this is where you need to look. Finally, the plane you have is not the best for a flat spin. Pattern ships are designed to be stable. The long tail is hurting you to a certain extent. You may never get it totally flat.
David