Mate, do you own CloD at all?
If yes, open a QMB and you'll see that we have an Early Spit I, called "Spitfire MKI" with a 2 pitch prop - I'm perfectly fine with this, perfectly suitable form pre June 1940 scenarios.
But we have another, late Spit I, called "Spitfire MKIa" which is exactly the same as our "Spitfire MKI" apart from the name. That one is supposed to have a CS prop!
And if we want historical naming, they should be called:
"Spitfire I" to "Spitfire IA (DH 5-20)"
"Spitfire IA" to "Spitfire IA (Rotol)"
As someone pointed it out above.