First it is well to know that all fighters are basically unstable. They have to have instability designed into them so they can be highly maneuverable. Just ask any full scale F-51 pilot if he ever took hands and feet off the controls for very long. Models of the full sized airplanes tend to acquire the habits, good and bad, of the 1'=1' scale aircraft. The balance is critical. The 51 gear is too close to the balance point. Most models even if scale have a "fudge factor" built into the gear so it won't land three point i.e. spinner and main gear. If you decide to shelve your 51 until you have more trainer time, good for you. Try to get a trainer with taildragger gear.
Best of luck