On August 5, 2000, at 0650 central daylight time, an experimental Thompson Avid Mark IV, N619T, was substantially damaged when it impacted the ground during takeoff climb. The 14 CFR Part 91 personal flight was departing the Flying Bar H Ranch, a private grass airstrip (2640 X 70 feet), with Gastons (3M0), Arkansas, as the destination. The airplane departed on runway 06. The pilot reported the grass on the runway was taller than normal, and that a tailwind existed at the time of takeoff. The pilot reported the takeoff roll was longer than normal and he was about to abort the takeoff when the airplane became airborne. The pilot reported he avoided a 60 foot tree at the end of the runway but was unable to gain airspeed. He reported he turned to the north but the airplane lost altitude and impacted into a hedgerow of shrubs. The pilot and passenger received minor injuries. Visual meteorological conditions existed and no flight plan was filed. The pilot reported there was nothing wrong with the airplane and that the engine was producing about 6,100 rpm's. He reported the airplane could not fly out of the tailwind and that it flew into a stall. The 0654 surface observation at Springfield Regional Airport located 12 miles from the accident site reported winds at 180 degrees at 9 knots.