IMPROPER PLANNING/DECISION BY THE PILOT-IN-COMMAND (PIC), WHICH RESULTED IN AN INADVERTENT STALL DURING TAKEOFF. FACTORS RELATED TO THE ACCIDENT WERE: THE EXCESSIVE GROSS WEIGHT AND IMPROPER LIFT-OFF BY THE PIC, THE PILOT/PASSENGER'S IMPROPER CREW COORDINATION REGARDING THE SPECIFIC INSTRUCTIONS THAT HE RECEIVED CONCERNING THE PAYLOAD LIMITATIONS, AND THE HIGH DENSITY ALTITUDE.