Dear Crumpp,
I just can't find these arguements compelling where you compare current peacetime FAA (US) procedures and definitions to the RAF in 1940, then state conclusions that are held and argued no-matter how they are contradicted by the rest of the evidence. I understand you have some background in (today's) civil aviation, it may be a good place to start but it is not producing very compelling arguments.
Plus there a lot of assumptions being put into your mix. Your current argument rests on implying new cylinder heads are needed (with consequent large requirements for time and materials), where AP1590/J.2-W (which you posted) refers to a rather more mundane "cylinder head spigot depth modification" (elsewhere referred to as a "top joint modification") which has aleady been done in routine maintainance or at the factory for new engines as Glider and others have said (document from March 40). It would be nice to see some more info on what exactly Merlin Mods 64,77 and 136 entailed (these are the cylinder head mods), but there are a lot of posted documents detailing that the airfield conversions were done very quickly.
The nature of the boost control modification itself rather argues against the relevance of comparing today's civil aviation standards with the 1940 RAF. Drilling extra air channels to convert an existing boost control cutout into a boost pressure setpoint control? Brilliant, ingenious, very seat of the pants. I have a little background in civil aviation too (Australia) and I can't see it happening today
I am not saying the devil's advocate role is not useful. I loved it when you totally offended the Spitfire purists by saying that according to a college course you did, the Spitfire fails control stability design standards developed in the US at the end of the war. There was an interesting point there that the pre 1940s belief that instability was necessary for manouverability was wrong...US engineers figured out that you can have both. This (correct) technical detail about changes in standards does miss the point though that pilots of the time (and today) found the Spitfire a delightful aircraft to fly.
There was also the time when you offended an ex-RAAF fast jet pilot (who also flew Yak 50s) by contradicting him repeatedly on flying in the "buffet", when you stated (correctly) that flight in the buffet regime is wrong because it represents a loss of aerodynamic efficiency and hence turn efficiency. But this (correct) technical detail misses the point that military or aerobatic pilots have often used the first point they can detect the onset of buffet (i.e flying in the "buzz") to stay in proximity to their maximum AoA...any slight deterioration in performance is offset by the ability to detect the point of departure and stay near it.
Bolding text and making statements that "this is a FACT" and "anyone that knows about aeroplanes would know this" I (and I suspect others) find very unconvincing. Generally you have used them to make statements that are correct within a narrow technical context or definition but then become misleading in the historical application to which they have been put.
Cheers, camber