The airplane was substantially damaged when it overran the grass runway and hit a ditch embankment. The pilot reported that on the final landing attempt he landed past a mower that had cleared the runway about 1/4 of the way down the length of the runway. He stated that he touched down past the halfway point on the runway and was too fast to stop on the grass runway, subsequently impacting the ditch embankment. The pilot reported no mechanical difficulties with the airplane. The tailwind component was calculated to be 5 knots.