Interesting to note tah this was recognised
Yes. Two years after the problem existed - I do have to wonder what supernatural powers of perception were required to note that Jerry piston engined fighters
were something like 100 kph faster at altitude than the Mark V suffering from poor production quality, but it kinda explains the deep curiousity of Air Intelligence reports about puffs of smoke emerging from German fighter exhausts in combat - maybe some secret Nazi black magic involving some exotic chemical addition..
or simply, as was the case, caused by the other guy giving full throttle..!
)
1) New satin-finish paints were introduced and
2) flush riveting throughout.
Oh, flush riveting, glad the guys at Supermarine caught up by the 1943 with the newest fashion.
How much was this an 'improvement' for the Spitfire's finish is strongly questionable though. The use of mixed riveting (flush riveting everywhere except for the fuselage) was decided early in the development in Spitfire after empirical tests (I think split peas were used on a scale model to measure the difference).
It was found that using convential dome rivets everywhere would cost 22 mph on the prototype compared to flush rivets; so flush rivets were used everywhere except for the fuselage, which was measured to only decrease speed
by 1 (one) mph. It was so insifignicant that using domed rivets on the fuselage was accepted as a (fairly good) compromise.
On the Mark VII/VIII and related airframes the rivets on the fuselage were replaced by flush rivets as well, increasing the top speed by a mighty 1 mph. Grand improvement, indeed.
Do you have information about how much these new paints were supposed to improve finish and performance..?
3) Production standards were improved. According to Shacklady and Morgan the first two refinements were introduced in late 1942-early 1943, before the Farnborough tests, which helped confirm what was already known.
Indeed and that's what the report says, that the new porduction Mark IXs from the summer 1943 (the report and preceeding reports are dated between June 1943 and September 1943) had 'some' improvement in equipment and build quality. Which is grand, expect for the fact that the most commonplace Spitfire for two years actually had the performance below that of the Spitfire I and Bf 109E of 1940, and the Mark Nines were still around in penny pocket numbers...