The razorback P51s were the fastest of the series owing to their better aerodynamics. The bubble top D models suffered because of turbulence behind the canopy which created more drag. They also suffered a loss of stability in the yaw axis which was partially addressed by the fillet on the vertical stabilizer leading edge. The H models and later TF 51s had higher v-stab and rudder assemblys to deal with this.

And please look closely at the "clean" configuration of the D in the tests posted by Former_Older, these aircraft had the wing bomb racks in place. Try to achieve these speeds with our in game P51D with the racks in place. LOL!!!

who cares about a few mph here or there? in rl almost no plane reached the specifications
which were set with new or at least good cared for planes.
@elaurens, see it that way that wear and tear is simulated ;-)

Actually those speeds are perfectly attainable in-game, the IAS read-out on the speed bar has an error(ask TAGERT If you don't believe me) I tested many planes in game for speed and climb rate and P51's were among to most correct ones in-game.
The P51B and C do reach the speeds mentioned and even surpass it but not by a lot, actually by a very low %, while P51D is in same error at alt as is the 190D9 '44
Generally I most certainly wouldn't say either P51B, C, or D in game is either overmodelled or undermodelled ;)

The P-51 as with most fighters in the game comply with real world data performance give or take a small %. The test are there to be done and you received some of the negative post you have because for years we have seen many complain and ask for a change but offer no facts, just assumptions.

S!

The Bs and Cs had the same yaw problem and many of them had the fillet added.
Not all the B/Cs received the -7 engine the D got. The -3 had a higher FTH than the -7.

The H also got an extended fuselage.