The pilot reported that shortly after takeoff, during the crosswind turn, the canopy opened. He continued to fly the airplane while trying to hold the canopy down with his left hand. The airplane porpoised, lost altitude, and the pilot was unable to achieve a stable attitude. He stayed in the traffic pattern, and, on final approach, he pulled the power off and stalled the airplane 4 to 5 feet above the runway, which resulted in a hard landing and substantial damage. The Pilot Operating Handbook (POH) stated that, if the canopy should open during takeoff, the pilot should not try to close the canopy and should continue the takeoff, climb to a safe altitude, and attain an airspeed of 65 knots. The POH then states that the pilot should continue to fly the traffic pattern, land, and, after stopping, close and lock the canopy. The pilot said the accident could have been prevented if he had kept the power on until touchdown.