Agree with the fuel reduction. I use 50 percent and the 51 does fly better.  Better, not like it should.  Likely a CG problem.  Most evident in pitch control even with the pitch slider full left.  Results in excessive stall warnings.
My fix to 3 US P51d: Aircraft.cfg open in Notebook.
[flight_tuning]
pitch_stability = 1.5

Save and test flight it.
Make a copy of the cfg file if desired.