Stability and Control characteristics of the Early Mark Spitfires

[Crumpp]

it was statistically established that, as soon as the longitudinal stability of the Spitfire was thus brought under control

Why don't you read the Operating notes for any early mark Spitfire.

"longitudinal instability" is used often....

I am sure the Spitfire Mark V increase in weight and speed caused an unmistakeable as well as difficult to ignore increase in in-flight break ups.