Throwing some light on rates of turn

[Crumpp]

Soooooo, why does the 109 E4 match the STANDARD DAY data at 5000 meters, but the Spitfire Ia and IIa are woefully short at 16,500 ft and 13,500 ft respectively?

Under what data are you looking at? What data are you using for these aircraft.

Are you looking at Indicated airspeed, TAS,..????

By my calculations, the Hurricane for example is within 2% of its data for a standard day. Whether that is optimistic or pessimestic depends on the weight of the aircraft in CLoD.