[Crumpp]

Let's have look to the early Spitfire C.G. (center of gravity) diagram:

That is not a Spitfire Mk I load plan and is not applicable at all. The NACA was well aware of the CG limits and capable of performing a proper weight and balance.

Read the Pilots Operating Notes as you posted:

14. This aeroplane is stable, and rock-steady in flight athigh speed. The controls are not ideal, because it will be found that the aileron control become exceedingly heavy at high speed, while the elevator remains comparatively light and sensitive. Individual aeroplanes vary slightly, but in most cases care is needed in the use of the elevator control at high speed, to avoid sudden increases of load factor, or "g". During a tight turn or loop in bumpy conditions, movements of the pilot's body due to bumps are liable to cause movements of the controls and so large and sudden fluctuations in "g". It is then advisable to press the elbow into the side to steady it.
...
(iii) Stability in pitch.- This aeroplane, though just stable in a dive, tends to be a little unstable in pitch (or foreand-aft) during turns; as the turn is tightened up so the elevator control tends to become lighter, or, at least, fails to increase in weight to a desirable extent. Therefore, care must be used with this control, especially in rapid manoeuvres. When flying in bumpy conditions at high cruising speed, the pilot's body is bumped severely on the seat, and this is very uncomfortable, even for a short time.

Aerodynamics wise there is no difference between these and still early version claims the Mk.II little unstable in pitch during turns just like NACA found out in their tests of the Spitfire VA. However, later revisions of the manuals claim these planes stable. So, what's the difference?

Bob-weights......