I've had two planes that would climb out of an inverted spin. One was a model tech .25 extra with an os 32/macs pipe combo, and the other is my current plane, a magic 3d with a tt36 heli motor. They would even do a decending flat spin into climbing flat or knifeedge spin.

With the extra, I would usually enter into it via a lomchevak, either at a 45 or vertical (sticks together, full throttle, down elevator, left aileron, right rudder). Plane would to 3 or 4 cartwheels/tumbles, and start into an inverted flat spin. As it descended I would move the aileron over to the right a lil bit, close to neutral, and try to maintain flatness of the spin, using throttle to slow the descent. At full throttle, the plane would stop its descent, do three revolutions, and then start to slowly climb. The hardest part there was to keep it from snapping over into a waterfall. Youre going to need to give it some aileron to keep it from rolling over, but have to work it in small increments

Just make sure ya have some altitude to recover, as well as a strong, RELIABLE motor. You might have to richen the needle up a lil bit on a 2stroke if its cowled, cause it tends to heat up with the lack of airflow across it. Probably the same for gas too, but I cant say for sure, I dont have a gasser yet.