The pilot’s failure to maintain an adequate airspeed and his exceedance of the airplane’s critical angle of attack, which resulted in an aerodynamic stall and subsequent spin. Also causal to the accident was the pilot’s failure to follow prescribed spin recovery procedures, which resulted in increased airspeed and airflow and the subsequent overstress separation of the right horizontal stabilizer. Contributing to the accident was the pilot’s inadequate preflight weight and balance calculations, which resulted in the center of gravity being aft of the limit.