On February 10, 1994, at 1113 mountain standard time, a homebuilt experimental Gansheimer Evans VP2 airplane, N187ES, experienced a thrust deficiency in the takeoff initial climb from runway 6L at Ryan Field, Tucson, Arizona. The aircraft subsequently stalled and mushed into the ground about 300 feet beyond the departure end of the runway. The aircraft was on the first test flight following construction completion and Federal Aviation Administration (FAA) certification in the experimental category. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft incurred substantial damage. The certificated private pilot, the sole occupant, was not injured. The flight was originating at the time of the mishap as a local area test flight. The pilot reported that the takeoff seemed fine until the aircraft got out of ground effect. The aircraft began oscillating in roll and did not want to climb. The pilot noted that the engine was producing full power throughout the sequence. According to the pilot, the aircraft "mushed back to the ground at 500 feet per minute" and impacted the ground in a slight nose- high attitude about 300 feet off the end of the runway. The pilot said he believes the roll oscillation was caused by an impending stall buffet and the lack of thrust was due to the propeller being of insufficient size.