S! Karnak
All the early Razorback D models were used in `43.
The D11 was the first model which came from the factory with Water Injection, but again, like the paddle blade on the D11, most D models were re-equipped with Water injection either shortly after they saw combat service, or even first thing that they arrived. If you read the USAAF test I posted in the Combat Theater board about the D5 vs the 109A5, you will note the D5 was equipped with Water injection despite not coming from the factory with it.
If HTC is determined to stick with what came from the factory, then I suggest the D11 with water injection and no paddle blade be used for the early Razorback D, and a D21, which came standard with paddle blade and water injection, be used for the January `44 onwards models.
Personally I think the simplest solution is to offer the D11 with and without Paddle blades. Then you have all the common models covered.
The D25 wasn`t in service until approx. July `44.