The pilot stated that after being cleared by the tower to taxi into position and hold on runway 30, the aircraft began to skid on the threshold markings. The right wing raised up and the airplane came to rest on the left wing and propeller. The winds were reported to be out of 300 degrees at 17 knots, with gusts to 30 knots. The airplane continued to skid off the runway onto the overrun. The pilot stated that he felt like he had taken every precaution and that the accident was a result of the gear sliding on the painted surface of the threshold which was slick in spots from an earlier rain storm. Probable Cause: The pilot’s failure to maintain control of the aircraft while taxiing for takeoff. Related factors were the wet runway and the gusty crosswind.