Re the radial engine trope.
This is one of the most enduring and questionable 'accepted wisdoms' that I too once believed. As a 20 something, I met and spoke to decorated FAA pilot John Blunden at some length on this subject. He'd flown both the Fairey Firefly and Hawker Fury in combat in Korea. I casually pondered why it was that the Fireflies were tasked more dangerous ground attack missions and not the Furies with their (as I supposed) more resilient radial engines.
He told me that the radiator is a very small target (and in the light of your comment Bill, not even visible to an aircraft attacking its victim from behind, so how are they even going to see it, let alone going to aim at it or hit it with 7.7s?!) - and was usually protected with armour, as well as being physically shielded about and behind from the structure of the aircraft and the engine itself. He also snorted with amusement and said that a radial engine is both a larger target to aim at than an inline for the people on the ground taking pot-shots (which is something I also have read regarding gunners aiming at 190s attacking B17s) and being bigger, even if there weren't cooling lines going into it, there were plenty of fuel and oil pipes just as likely to get hit and bu&&ered and cause an engine failure as on an inline which had a much small frontal profile, even including the radiator.
Again, I get most of my perceptions or "value judgements" on these matters directly from the operational histories and the interviews and memoirs of operational aircrew, i.e. mainly pilots.
I don't think this is a trope, and once again, I do not appreciate being baselessly accused of spreading tropes.
Whether or not a radiator is a small target depends on the layout of the radiator and cooling systems. If the cooling systems are concentrated in the nose, it is a relatively small target. If the cooling systems extend into the wings, as they were in many aircraft, it is a bigger target.
The Ki-43 and A6M pilots in particular emphasized shooting into the radiators and cockpits of Allied fighters. They had specific techniques for doing it, for example, A6M pilots would pull into a tight loop, which no Allied fighter could follow. As the Allied fighter stalled out, the A6M pilot would continue the loop, while slipping with the rudder, and shoot into the nose of the Allied fighter from above. The Japanese called this "Hineri Komi"
This was not the only means by which this was done. Japanese fighters generally had a better rate of climb, especially at lower altitudes, than Allied fighters, and they were often able to attack from above, or during tight turns while pulling lead.
What is more, Allied pilots commented on the issue of radiator vulnerability as well. When the P-51A was introduced into China, 23rd Fighter Group leadership was very impressed with it's speed. But they found several small problems, one of which was the greater vulnerability of the radiator, both to ground fire and to fighters. The P-51A took greater losses in that theater than the older, slower and less sophisticated P-40 - which had the radiator plumbing concentrated in the nose.
Besides all, if you were really in such an advantageous position as to aim at a radiator, why wouldn't you instead be firing through the unarmoured sides of the cockpit or canopy to take the pilot out?
They generally attempted to do that as well, spraying the cone of bullets into the 'nose', from what Saburo Sakai and others described. This is also what was done by Hans Joseph Marseille in North Africa against P-40s and Hurricanes.
The subject has cropped up several times elsewhere too and no one ever seems to have been able to resolve the evidence in favour of the radial. It would seem odd, if its really true, that IL2s, the most wisely used ground attack aircraft of the war, were never equipped with a radial engine, given the environment in which they operated (The Russians had them, afterall). And also on the western front, given the Hawker Typhoons were operating with an inline engine of already tainted reliability, there should have been a marked and measurable difference of loss and attrition between them and the P47s performing a very similar mission.
I summon the Myth Busters on this one!
The Il-2, you might want to notice, had an armored 'bathtub' protecting the whole engine and pilot area (though not the poor gunner). I think the Typhoons got some engine / radiator armor too when they started using them for ground attack (greatly increasing their weight to overall detriment)