ACCORDING TO WITNESSES, THE PLT TOOK OFF ON RWY 4, THEN TURNED LEFT TOWARD THE SOUTHWEST & FLEW PARALLEL WITH THE RWY AT A DISTANCE OF ABOUT 1/4 TO 1/2 MI. HE LEVELED THE ACFT AT APRX 200' AGL, JUST BELOW THE CLOUDS, UNTIL APRX ABEAM OF MIDFIELD, THEN HE TURNED SLIGHTLY TO THE RIGHT. ONE WITNESS REPORTED THAT AT ABOUT THAT TIME, THE ACFT WAS 'BUFFETING OR PORPOISING.' ANOTHER WITNESS, WHO WAS DRIVING SOUTHBOUND ON I-95, ABOUT 3/4 MI EAST OF THE CRASH SITE, STATED HE SAWTHE ACFT ON A WESTBOUND HDG, CLEAR OF CLOUDS, AT AN ALT OF 200 TO 300 FT AGL IN APRX A LEVEL ATTITUDE, WHEN IT SUDDENLY 'NOSED DOWN' TO THE GROUND. THE ACFT IMPACTED IN A RESIDENTIAL AREA WHILE IN A STEEP DSCNT. NO PREIMPACT MECHANICAL PROBLEM WAS FND. THE ACFT WAS ESTIMATED TO BE APRX 600 LBS OVER ITS MAX GROSS WT LIMIT OF 5400 LBS WITH THE CG .27 TO .97 INCH BEHIND THE AFT LIMIT.