Spitfire prop pitch and radiator question

[JtD]

Mastiff, for performance evaluation you need to look at TAS, from the yellow gauge. All the data you find is typically TAS, and if it is IAS it has so many errors to it that you cannot compare it to what you see in game.
Also, the Spitfires were tested radiators closed, which is something you can't do in game because it is an automated radiator. You'd need to fly on a very cold map, but then the performance would be wrong because of the coldness.

Generally, you can expect that planes with a recently reworked flight model have as accurate performance as possible in the game engine. It's more a matter of knowing which data was used for reference, there usually is a wide range available, and therefore the flight model can't match all of it.