On February 5, 1998, approximately 1455 Pacific standard time, a Bromley Steen Skybolt homebuilt aircraft, N55740, registered to/being flown by a commercial pilot, was substantially damaged during an undershoot and loss of control on landing at Stark's Twin Oaks Airpark, Hillsboro, Oregon. The pilot sustained minor injuries. No flight plan had been filed and visual meteorological conditions prevailed. The flight, which was personal in nature, was to have been operated under 14CFR91, and originated from the accident airport approximately 1450. The pilot reported that after takeoff he remained in the traffic pattern and that he "was too low on final approach and (the) wheels struck (the) slope leading to (the) end of (the) runway." The landing gear then collapsed and the aircraft skidded down the runway on its belly during which it slid off the west side of the pavement. The airport manager reported that tire marks from the aircraft were observed approximately 30 feet short of the paved physical end of runway 02. Runway 02 has a painted displaced threshold of 100 feet (north of its physical end). A witness reported that the aircraft bounced and then re-landed on the asphalt surface during which the left wingtip and propeller struck the ground. The aircraft then veered left off the west side of the runway and rolled down the dirt embankment upon which the runway is built up on, coming to rest in the mud. Winds at Hillsboro airport, located six nautical miles north, were reported at five knots and variable direction at 1450.