The pilot of the tailwheel-equipped airplane reported in a written statement that, after a "successful pre-check," he initiated power for takeoff and once airborne, "the plane was losing power enough that [the] plane would not clear [the] tree line at the end of the runway." He added that, about 10 ft. above the runway, he aborted the takeoff by "throttling back" and made a hard landing on the grass runway. The pilot reported that during the landing, the main landing gear collapsed, and the airplane slid for about 50 ft. on the runway before stopping. The left wing, fuselage, and engine mounts sustained substantial damage. The Federal Aviation Administration (FAA) Aviation Safety Inspector reported that, about 3 weeks after the accident, the pilot called him to add to his original statement. According to the inspector, the pilot reported that the engine was not losing power, he overacted to the situation, and put the airplane back on the ground too quickly. The pilot further reported that, the airplane was not gaining altitude because he didn't give the input to the elevator at a fast enough rate to execute a proper takeoff. The FAA inspector added during a telephone conversation with the NTSB investigator-in-charge, the pilot reported that, he rotated at the speed he normally does when single pilot, but during this flight he had one passenger on board. The pilot failed to submit the NTSB Form 6120.1 Pilot/ Operator Aircraft Accident/ Incident Report and did not return the phone calls from the NTSB investigator-in-charge.