According to the pilot, he utilized the checklist and set elevator trim to "almost neutral" with one notch of flaps for departure. During the takeoff roll, the pilot felt that the airplane wanted to lift off earlier than he was accustomed and he had to hold the nose down. When the pilot finally rotated the nose, the airplane "jumped up quicker than normal" and he kept the nose down. After the airplane began to increase airspeed and climb, the pilot raised the landing gear. The pilot then felt a gust of wind, and the airplane drifted to the left. The pilot corrected the airplane back to the runway heading, but it then began to descend. He pulled the power back and landed the airplane gear up on the grass airstrip, resulting in substantial damage to the lower fuselage. The pilot reported no preexisting mechanical anomalies that would have precluded normal operation. He also reported the wind as being from 20 degrees to the right of the runway at 14, gusting to 22 knots. According to a representative of the airplane manufacturer, landing gear retraction takes 3 to 6 seconds, and during the process, movement of the inboard landing gear doors creates additional parasitic drag. He also noted that in previous cases, pilots have taken off at lower airspeeds than normal then retracted the landing gear, which resulted in the airplane's settling back down to the surface instead of climbing.