The pilot was conducting circuits and landings to gain additional experience on the aircraft type. He had already flown three circuits and had experienced some difficulty remaining behind slower traffic. On the fourth circuit, the Tower advised him to turn inside a slower aircraft ahead which caused a shortening of the downwind leg of the circuit. Because of the number of aircraft operating in the circuit the pilot decided to discontinue the flight and advised the Tower he would make a "full stop" landing. However, due to the distraction of other traffic and concentrating on slowing the aircraft for landing, the pilot forgot to extend the landing gear. The aircraft slid to a stop on runway 29 Left , sustaining damage to the underside and propeller.