The Mk III was abandoned in favour of the Mk V which was a much simpler job to do. Essentially bolting a modified Merlin XX onto a Spitfire I air frame was seen as more expedient, and the Mk V was a successful aircraft.
The Mk III was far from perfect, there were problems with cooling and chopping three and a half feet of each wing, reducing wing area to 22o sq. ft. had an adverse effect on handling. Boscombe Down noted that 'turning performance at heights from 20,000 to 35,000 feet show rapid deterioration in manoeuvrability'.
Dowding didn't like the clipped wings either, fearing it made the Spitfire resemble he Bf 109 more strongly, 'a matter in which mistakes have already been made'. He asked for 'a pair of ordinary wings' to be fitted to the prototype. He was also concerned about the 'dangerously long' landing run of the new version.
As ever, tinkering with a successful design is never as easy in practice as it is in theory!
Cheers
Steve
Bad luck too, the first prototype wings (from memory) were destroyed in a bombing raid. But it was shortsighted in that the 109 was seen as the only German fighter to compete against and they were in the 'altitude race' of the time, yet they did have enough intelligence to know something else was coming along. Moever as the RAF moved onto the offensive it did not take a lot of thought to realise that the fighing would move to where the bombers were (around 15,000ft at the time).
it was a bad allocation of Merlin XXs to put them in Hurricanes.
Part of the problem was that there was no clear stategic plan, direction or foresight. Leigh Mallory's 'leaning yowards the enemy'was an expensive disaster, especially when the need for Spits was in Malta and North Africa that was where the real battles were.
So the Spit V matching the 109F seemed 'right' to them, they thought they'd just fight the BoB again over France and the Luftwaffe would fly up to get hammered. It didn't happen and it was Fighter Command that got hammered.
If the Merlin 60 series had not been available...... Rolls Royce pulling the RAF's chestnuts out of the fire again. Naturally it was RR that fitted the first trial 60 series in a Spit on their own intiative (Hives had little patience with MAP and the rest).
The other problem that a LR Spit was killed by Portal so they had no way to actually fight over Europe as they didn't have the range.
They should have put heaps into Malta and NA far earlier, where they could fight the Luftwaffe and damage it amd make a strategic difference. Instead they left it to Hurricanes and P-40s and the pilots they suffered accordingly as did the people and troops on the ground.
The Mk III also should have gone ahead (wth std wings) even if just because it had far more scope for development with better Merlin XX series engines known to be coming along (remember the 60 series was barely a concept back then in late 40 and early 41). On the same engine power it was at least 10mph faster, maybe as much as 20mph and a far wider fighting altitude range.
41 and 42 was when Fighter Command was stuffing up by the numbers and it is hard to pick anything they did right.