If I may offer a couple of observations...Major Tom, the Torque reaction of any engine/prop combination is always that provided by the engine, it cares not whether thrust is produced or not, if the stick in front is being rotated at an RPM then there will be torque, and it will be determined by the engine power and RPM. A glance at the engine torque/power curves will provide you with the torque at the RPM your engine is running. This does not change regardless of the prop, if the engine is running at an RPM, there will be an equivalent torque. As for the yaw associated with rapid power changes at low speeds, this also happens at any other speed, but is less noticeable due to the greater dynamic pressure on the flight surfaces. Consider the case of the F4U, it did not get its carrier wings due to the massive torque effect of the engine/prop at 'go-around', which could, and did ROLL the airplane into the ocean when a baulked landing was attempted. The only cure for this, at low speed, was the massive fin offset. Why, you ask. Basic aerodynamics. At low speed if you try to counter torque roll you risk stalling the wing on the down going aileron side. The drag increase and loss of lift if the wing stalled would dump you unceremoniously into the drink. Now as a full size pilot you all know that that at low speed, approaching the stall you maintain balance with the rudder, ie yaw. Model pilots with heavy models will tell just the same thing. I offer this explanation, to counter the roll caused by the engine torque, one side of the wing must be producing slightly more lift than the other, and therefore, just a bit more drag. This drag is countered by rudder as the drag would tend to manifest in a yaw toward the wing producing the extra lift. Low speeds and high AOA would simply magnify the effect until as the stall is approached, any rapid increase in torque (power) may result in the inability of the wing to provide sufficient lift to counter the effect, and the wing starts to drop on that side. As with the F4U, any addition of aileron will not help, and only application of rudder (in the slipstream too) can assist. I can think of no other likely explanation.
Evan, WB #12.