I realize that the P-51 CoG was moved but,

[MaxGunz]

Have you tried UDPGraph or UDPSpeed?
You can run them on ntrk playbacks. It was using UDPSpeed that got me a great appreciation on the range of starts even given alt and start speed not just on my own tests but tracks that were sent to me. To compare dives I had to find speed matches well after the beginning rather than trying to match times. Once I got two planes at the same speed and close in alt I was able to get some idea of acceleration in dive differences. It's not much until the slower one gets near top speed and then the walk-away commences.