The pilot reported that during takeoff on runway 12, practicing a short field maneuver, the aircraft encountered a gust of wind. The pilot was unable to maintain control and the aircraft traveled off the side of the airstrip and collided with a fence and trees. The pilot further reported that the airstrip terrain rises steeply on the north end of the strip. The takeoff roll was initiated at the high point and "...not perfectly aligned to take off down steep hill..."