snaught,
When you input for negative "g" forces the rudder reverses. Most likely what happened is you input down elevator with ailerons and rudder in the same direction which is the transition for an inverted flat spin. Then changing the elevator to down puts it into a knife edge spin. This makes for great fun when you change from one to another kind of spin.

To better understand what happens with the rudder try this:

1. Place the plane in a stand inverted. Stand behind the plane to observe the control inputs.

2. Input down elevator / left ailerons / left rudder
Observe the elevator is "Up"
the rudder is "Right"
the wing on your left has the aileron "Up" (so roll is
still to the left)

3. To correct the above "negative g" just reverse the rudder (in
the case above use right rudder which will move it to your left)

Additional control input information:

Positive spin or snap roll: Up elevator and ailerons/rudder in the same direction.

Negative spin or snap roll: Down elevator and ailerons/rudder in OPPOSITE directions.

The above information is given as a basis for learning these maneuvers. There is much more information regarding this (literally volumes). Start with this and keep looking in here at RC Universe.

EXCAP232