Remember from the content of the show, that this was during the Battle of Britain, and the Spits involved were equipped with 8x .303cal MGs...not the later war .50cal MGs and 20mm HS Cannons.
In these small rifle-caliber MGs, the velocity and energy of the individual bullet falls off very quickly beyond about 300-400M. By staying close-in, more of the kinetic enegy is delivered to the target, rather than lost due to aerodynamic drag.
Also, accurate gunnery is easier to acheive when closer to the target, and you don't have to worry as much about things like tracer burn-out, and ballistic trajectory arcs. In combat, simpler is always better.
Interesting that the winner of the training fly-off squeeked by on the subjective evaluation of the instructors; in that he had a better and more natural "feel" for the aircraft than his competitors.
In their view, he simply "knew" when he was making a mistake, was able to describe the mistake to his instructors & take the steps necessary to correct the mistake, and never made the same mistake twice.
In regards to the rudder trim, I don't recall the context precisely, but I think he was using it as a defensive technique not an offensive one.
From what I recall, I believe he was using the trim to cause the aircraft to fly in a crab-wise attitude "hands-off". This would force him to constantly be applying a bit of corrective rudder pedal input in normal maneuvering.
I'm unsure, but did he believe this would give him an edge and allow him to be a more difficult target for anyone engaging from directly behind, or was it simply a technique to allow him to clear the the horizontal and vertical stabilizers upon bail-out?
I didn't quite get his point I guess.
CptA