cant speak for the PA31-325 Navajo, but over 1000hrs on its bigger sister PA31-350 Chieftain, what a lovely aircraft, flown for "old" Airlink, and when operated within W&B limitations would perform as per the AFM.
One of my fellow PA31 Capt's had a magneto shaft failure (common shaft supplying both magneto's) after take-off at JNB, with a full load, and he climbed out and flew it all the way to a single engine landing, with a full load of pax and baggage...at MAUW
critical was getting the "barn door" cowl flaps closed ASAP on the dead engine, and not flying even slightly overloaded, and as also mentioned the CofG must also be right.