IMPROPER PLANNING/DECISION BY THE PILOT, WHICH RESULTED IN HIS FAILURE TO ATTAIN SUFFICIENT AIRSPEED FOR A CLIMB PROFILE. FACTORS RELATED TO THE ACCIDENT WERE: THE PILOT ALLOWED THE WEIGHT AND BALANCE OF THE AIRCRAFT TO EXCEED THE CERTIFIED LIMITS, HIS USE OF EXCESSIVE FLAPS AND IMPROPER LEANING OF THE MIXTURE FOR TAKEOFF, AND HIGH DENSITY ALTITUDE.