As soon as I move my peddles, I get deflection motion at the rate I scaled the rudder to slow down an almost instant slap to full deflection by removing 17000 from each end of the potentiometer scale line. That is sitting on the runway and watching it deflect as I push the peddles. As for in flight, who knows unless you are trying to start the opening salvo with Hitech to convince him he has something with the P51 wrong and this is post v1.00 in a long campaign.
Just copy off your rudderpeddlebrandname.jsm file as a backup. Then edit the active one in notepad and change the first number to 10000 and delete 10000 off the last number which will change it to 55535. Then up your P51 offline and watch your rudder peddle deflections. Depending on the brand of rudder peddle, the line will either say "rudder", or "z axis", or "slider", or "z rotation".
Other wise if it is that finger toggle in Siatek throttle quadrants, or a twisty stick rudder, I think it says "z rotation" for the twisty and "axis-yaw" for the finger toggles. Or do a calibration where you only partially deflect it in both directions and compare the lines to the backup file. And you always have the backup file to put everything back where it was.
I get the feeling you don't want to do something this simple and hope others will and report back instead. Just back up the jsm file and you cannot hurt anything.
And it's not a fix for your issue, I resorted to it after noticing with my CH Fighterstick in AH2 I was not getting a full right aileron deflection with the P51D even when I repeatedly calibrated. I just happened to notice that by accident offline one day. So I cropped the ends of the calibration lines and suddenly got a full deflection with less wrist input and faster deflections to full stop. So I applied it too all of the axis calibrations. I've never had to replace springs, potentiometers, or calibrate since. I didn't bother to test other planes for the lack of full deflection since, after I cropped the ends of the line, all planes had great and fast deflection on all axis. I may have a bad pot in my flight stick and this accounted for the bad pot for all I know.
And I had to learn a lot about scaling so my spi16 would stop snapping over into the ground when I got low and slow in furballs. Full deflection in half the joystick arm throw is very powerful and a great way to end up in the dirt if you don't understand scaling. You need to slow down the intial 1\3 of the rudder movement for fine control on taxi, takeoff and those micro deflections to help lineup targets. And so your GV doesn't fling itself from side to side just touching the rudder. Yeah sounds like a lot of work to fix a perception.....