The CO of 264 was very reluctant to follow the official line, that the combat trials were not considered by the RAF to be representative and doubts were being raised in Jan 1940 as to how well it would do in day fighting. In view of what happened I can only say that the doubters were right to doubt.
Yep, you are absolutely right, they were right to doubt; the thing is, the Defiant was not designed for the purpose of attacking single seat fighters, but it was employed in that role. Hence my comment about misappropriation of resources in another thread. Yet, despite a couple of bad days (264 Sqn suffered six shot down on one day too, but no lesson was learned) the Defiant continued to be used in a role it was not designed for. Clearly as these documents show, there was doubt about its speed in the face of the enemy, yet apart from Sqn Ldr Hunter's efforts, nothing was done officially to change its tactical use in the battle. This is not the fault of the aircraft, as obvious as that statement is.
Bearing this in mind, the Defiant did not do anywhere near as badly as is always assumed. Your statement of "loss rates through the roof" is a bit of an exaggeration considering only 14 aircraft were lost in combat in those 174 sorties, regardless if they were all combat sorties or not. Read my earlier post; on papr it looks worse than actual numbers suggest, but 14 lost in a month is not comparitively high losses at that time. As a percentage of a single squadron, yep - looks real bad on paper.
Yes, I agree with you that the Defiant should not have been used in the roles it was, convoy escort, standing patrols, yet, throughout the time it was - that is the fault of Fighter Command for ignoring the signs i.e. your documents - especially the last line of the January one! My second point is that losses of Defiants were not as high numerically as assumed by comparison to other types and the type fared better than you give it credit for. Yes it was slower than single seat fighters, but no more vulnerable than any other fighter if the tactics 264 Sqn employed were used. Actual combat proves that.
Regarding Sqn Ldr Hunter's reluctance to follow the official line - why would he? the tactics Defiant crews were trained to use against bombers clearly wouldn't work against fighters! His actions saved the lives of his squadron mates! Almost all RAF pre-war tactics were found wanting once the shooting started - squadrons were left to their own devices to adopt tactics based on their experiences, this is why Sailor Malan put out his Ten Rules of Air Fighting; this wasn't an edict from up above, this was a commander concerned about the high losses his troops were suffering. Again, the reason why RAF units adopted the Finger Four formation was because combat experience that proved that the Vic formation was unwieldy. This is also why indidivual airmen synchronised their guns to meet at a much closer range than what was officially specified and fitted armour plating behind their seats. These didn't come from official sources.
There was no substitute for experience; Hunter was smart to trial these tactics - wouldn't you if you were in his position? They were employed in combat and proved successful - no better endorsement than that. 141 Sqn's CO refused to listen to Hunter when they met after the squadron was declared operational in May 1940 and it cost him and his squadron dearly.
As for that January document, as you are well aware, interception speeds need to be high, but combat descends and speed bleeds off - the Defiant proved on a number of occasions that it could successfully intercept and destroy unescorted bombers by day - the role it was designed for. On 27 May 1940 264 Sqn encountered a formation of 12 He 111s and shot down three of them and damaged a fourth without loss to the Defiants.
Interesting documents though Glider, thanks for sharing. Since I am in New Zealand it's kind of hard for me to gain access to material about the Defiant from official sources. I am keen to get hold of documents that outline when and why (yes, I know why, but offically) the Daffy squadrons were withdrawn from day ops.