Interesting tests, Alex. Keep it up!
Talking about the Corsair photo
You are correct to point out the rudder.
However 'p-factor and gyroscopic precession' are NOT in play. So the point you make re the rudder is even more valid re 'SSS'.
The p-factor and gyroscopic precession only come into play during pitch and or yaw changes.
The torque is in play but that is transferring into the deck via the UC.
I can assure you that P-factor, gyro-P and torque are all at play in straight & level flight at all speeds. Any tri-gear (nosedragger) prop plane, single or multi-engine, Cessna 150 to P-63 to King Air 350 twin turboprop, will turn hard left if right rudder is not applied at takeoff. The Cessna 421 I fly will not stay on the runway if full power is rapidly applied, even with full right rudder, or if powered up with brakes on, and then released. For that reason, we slowly add power for 5-8 seconds while rolling to give the rudder more authority after 40 knots or so. Same thing in descents, we must use left rudder to correct for P-factor with the nose low.
The Corsair was one of the fighters that was powerful enough to roll over on the ground if power was abruptly applied, and this killed more than one Naval/Marine aviator.