The pilot planned to conduct a post-maintenance test flight in the vicinity of the departure airport. The pilot initially reported that the takeoff seemed normal at first, but as it progressed it began to feel “sluggish.” When the airplane was about half to three-quarters of the way down the runway, he observed an indicated airspeed of 62 knots, and became concerned the airplane was not performing correctly. He elected to abort the takeoff, retarded the throttle and applied brakes. The airplane continued past the end of the runway, veered into grass, and impacted a perimeter fence, which resulted in substantial damage to the airplane’s left wing. A review of recovered data recorded by the onboard avionics showed that the airplane accelerated to an indicated airspeed of 85 knots before it began decelerating. The pilot, after reviewing the recorded avionics data, acknowledged that the engine developed full rated power throughout the takeoff roll, and that the airplane accelerated normally prior to the abort decision. He also reported that there was no glare that would have impacted his ability to observe the primary flight display’s airspeed indicator. The pilot also stated that there were no preimpact mechanical malfunctions or failures of the airplane that would have precluded normal operation.