The pilot, accompanied by a passenger, was departing from an airstrip which had a dry short grass surface, aligned in an east west direction, and located on the top of a lightly timbered hill. The weather was reported as being fine, with a gusty 10 - 15kt wind blowing from the south west. The pilot stated that he had ascertained the crosswind component was within the limits for the aircraft before commencing a take off towards the west. He reported that the engine power and acceleration were normal, but after becoming airborne he noticed the aircraft appeared to be sluggish, and slow to climb. The automatic wing slats had deployed indicating the aircraft was at, or near its stall speed. He had difficulty maintaining directional control, and the aircraft veered to the right. He considered rejecting the take off, but as the aircraft was moving with a sideways motion he decided to allow it to accelerate in ground effect rather than chance a landing which may have impose a side load to the landing gear, and the possibility for it to collapse. The pilot believed the wind gusts increased and changed to a tailwind component, further reducing the aircraft's climb performance. As the aircraft departed from the airstrip area the pilot was unable to arrest the sideways drift before colliding with a tree. The aircraft was extensively damaged, and the pilot was unable to turn the fuel off as the selector was inaccessible due to airframe distortion. He evacuated himself from the rear cockpit, then assisted the passenger to exit from the front cockpit. During the evacuation smoke was observed around the front cockpit floor area, which originated from fuel contacting the hot engine and exhaust. The aircraft then became engulfed in flames, resulting in an extensive grass/bushfire. It is possible that the pilot raised the aircrafts tail too soon at the commencement of the take off run before effective rudder control could be established. The propeller slipstream direction allows the wash to contact the right side of the rudder imposing a tendency for the aircraft to swing right. This would have been aggravated by the aircrafts slow forward speed, and the crosswind from the left. The slow airspeed, crosswind, and/or the reported wind changes, would have caused difficulties for the pilot to maintain and/or recover directional control.