George,

You may wan to try an Inverted flat spin. Some planes that wont go flat upright will inverted.

Start inverted, power at about 1/4 and as the plane slows push left aileron, right rudder and full down elevator all at the same time. This should give you and inverted spin. Leave a little throttle in to tighten up the spin. As it starts to tighten up slooooowly move the aileron to the right. A little at a time. if its going to do it you'll have to figure out just how much aileron to add to flatten it out.

Aft CG helps if you are comfortable with playing witht he CG of your plane.

Hope it helps.