TAKEOFF WAS AT NIGHT WITH A VEHICLE POSITIONED AT THE DEPARTURE END OF THE RUNWAY AND ITS HEADLIGHTS SHINING TOWARD THE AIRCRAFT DURING THE TAKEOFF ROLL. THE AIRPLANE APPEARED TO TAKE AN ABNORMALLY LONG TAKEOFF ROLL. THE AIRPLANE WAS THEN OBSERVED TURNING AND SETTLING INTO TREES. IT IS ESTIMATED THAT THE AIRPLANE'S FOWARD C.G. LIMIT WAS EXCEEDED BASED ON THE PILOT'S AND FRONT SEAT PAX'S WEIGHT. THE PILOT HAD NO USEFUL VISION IN ONE EYE. THE PILOT HAD PREVIOUSLY FLOWN THE AIRPLANE ON ONE MAG ON MORE THAN ONE OCCASION. THE MAG SWITCH WAS FOUND IN THE RIGHT MAG POSITION.