ORIGINAL: Ed Cregger
When inverted, right thrust becomes left thrust, thus pulling the climbing model (assume an extended vertical ascent) to the left, which torque and P-factor are already trying to do. I use zero-zero and learned how to fly the model through these shifting modes.
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True, but note that when inverted, the vertical stabilizer/fin "moves" to the "bottom" of the fuselage. Where the original right-thrust was counteracting the left-yaw induced by the interaction between the spiral prop-stream and the upward-extending vertical fin; the inverted "left"-thrust is now properly counteracting the "right"-yaw induced by the interaction between the spiral prop-stream and "downward" vertical fin.
Free-flighters have long known that moving the vertical fin from "above" to "below" the engine thrust-line will change a power-on left-turn into a power-on right-turn.