On April 1, 1994, at 1354 mountain daylight time, a Piper PA-24- 260, N8961P, sustained substantial damge during cruise near Roswell, New Mexico. The private pilot and the sole passenger did not receive injuries. Visual meteorological conditions prevailed for the personal cross country flight. Air traffic control data indicated the airplane was 35 miles southeast of Roswell, New Mexico, at 10,000 feet MSL en route to Albuquerque, New Mexico, when the pilot reported "severe downdrafts." The airplane entered an uncontrolled altitude deviation and descent. Recovery of airplane control, as reported by the pilot, was 4,400 feet MSL. The flight diverted to Roswell, New Mexico, and landed without further incident. An examination of the airplane by the pilot and a mechanic (statement enclosed) reported the horizontal stabilizers were bent downward. The pilot reported that he closed the throttle as the speed approached the never exceed speed; however, the speed continued to increase.