The most important aspect of air-combat is surprise (typically by aircraft with an altitude advantage) as most aircraft that are shot down never see their attackers.Outnumbered doesn't seem to usually make that much difference for the Ki-43s or for other Allied types. Being bounced sometimes does, especially if one side didn't remember to post top cover. Early warning was clearly a factor which greatly assisted AVG / CATF / 23 FG etc., and sometimes the Japanese too as they appear to have had early warning radar in some areas.
The JAAF pilots also mention in the book targeting the nose of Allied fighters, to get the radiators. They also targeted the cockpit. On a Hurricane there is a fuel tank in front of the pilot which is also vulnerable. This is, in part, how they were able to take out Hurricanes and often many other types, including bombers, so quickly on numerous occasions. I'd say it's evidence for something I've been suggesting for a long time, nose guns tended to be more accurate than wing guns.
It's also notable that the Ki-43 pilots did not seem to hesitate to go head to head with many Allied aircraft.
"FIGURE 3. BOOM AND ZOOM, OR AMBUSH TACTICS
Surprise usually results from one opponent having an immense advantage in SA [Situational Awareness]. There are a number of definitions of SA, but one widely accepted definition summarizes SA as, "keeping track of the prioritized significant events and conditions in one's environment."10 Therefore, aerial combat can be viewed as a competition, or battle, for superior SA. Aircrew obtain and maintain SA through the use of their own senses, training, and experience to interpret inputsfrom the surrounding physical environment, aircraft displays, and communications from friendly offboard sources. More modern detailed analysis of 112 air combat engagements during the Vietnam War conducted by the U.S. Air Force (USAF) in the 1970s concluded that 80 percent of aircrew shot down were unaware of the impending attack. Surprise, the tactical outcome of superior SA, is so important to success in air combat that it is assumed in the modern USAF air combat mantra of "First Look, First Shot, First Kill." Despite vast changes in aircraft, sensor, communication, and weapon capabilities over the past century, the fundamental goal of air combat has remained constant: leverage superior SA to sneak into firing position, destroy the opposing aircraft, and depart before other enemy aircraft can react."