7-SEAT ACFT TOOK OFF WITH 4 ADULTS & 8 CHILDREN ABOARD. ACFT ROTATED AT ABOUT 2000 FT DOWN RWY & CLIMBED IN A FLAT NOSE HIGH ATTITUDE BEFORE SETTLING INTO 30 FT TREES ABOUT 4223 FT FROM POINT OF LIFT-OFF. ACFT OSCILLATED VIOLENTLY 2 OR 3 TIMES IN THE PITCH AXIS DURING THE 20-30 SEC FLT. ACFT WAS ABOUT 445 LBS OVER MAX GROSS WEIGHT & CG WAS 4.26 INCHES AFT OF THE AFT LIMIT. ON 6/9/82 THE PLT TOOK A CHECKRIDE TO HAVE A "CENTERLINE THRUST ONLY" RESTRICTION REMOVED FROM HIS MULTI-ENG RATING. 59 OF HIS 62 HRS MULTI-ENG WERE AS COPILOT. HE HAD NO FORMAL C-414 TRAINING & HAD RECD ONLY 2 HRS OF INSTRUCTION IN CONVENTIONAL MULTI-ENG ACFT. HE HAD NEVER BEEN REQUIRED TO PERFORM WT/BAL COMPUTATIONS IN HIS MILITARY FLYING OR ANY FAA EXAM OR CHECKRIDES. CO MANAGEMENT DID NOT COMPLY WITH INSURANCE STIPULATIONS WHICH REQUIRED PLT OF THEFLT TO ATTEND A CESSNA FLT TRAINING SCHOOL, NOR DID THE PLT SATISFY THE MINIMUM HR REQUIREMENTS. FAA CERT EXAMINER LOST CERT ON 7/10/82, HISTORY OF INCOMPLETE OR SUBSTANDARD CHECKRIDES. OCCUPANTS DIED OF THERMAL BURNS & SMOKE INHALATION.