On June 23, 2004, approximately 0945 Pacific daylight time, a Piper PA-20, N699DS, was substantially damaged following a main gear collapse while landing at Deer Park Airport, Deer Park, Washington. The private pilot, who is the registered owner of the airplane, and his flight instructor were not injured. The local 14 CFR Part 91 instructional flight, which departed the same airport about 30 minutes earlier, took place in visual meteorological conditions. No flight plan had been filed, and there was no report of an ELT activation. According to the pilot/owner, he had previously received a tail wheel endorsement, but had not utilized it for a number of years. He said that he was currently working with an instructor to regain his proficiency, but that the flight instructor chose to fly in the left seat because the airplane only had brakes on that side, and it had been awhile since he had instructed in a tail wheel aircraft. On the second touch-and-go of the day, the owner made an approach with the intent to do a three-point landing, but inadvertently allowed the airplane's main wheels to contact the ground first, resulting in a bounce. The airplane then touched down in a three-point attitude and began to swerve to the left. The owner applied right rudder, but could not stop the turn. Seeing that the owner was having difficulty, the flight instructor took control of the airplane and attempted to correct the situation by applying "full" right rudder, right brake, and left aileron. The instructor was unable to arrest the left turn, and subsequently, the right main gear collapsed, and the airplane came to rest on the runway. The pilot said that there did not appear to be any malfunctions or anomalies in the flight control or rudder systems, but that the aircraft was very sensitive to control inputs during landing and takeoff. He said that flying from the right side of the aircraft, which was something he had not done before, made it harder for him to effectively control the aircraft. He said that after he purchased the aircraft, he flew for about two hours with other instructors, both of whom mentioned that the aircraft was very sensitive to rudder inputs. He therefore had the aircraft's wheel toe-in checked. During that inspection it was determined that the toe-in on one wheel was incorrect, so the owner had the setting corrected. About the same time, the alignment of the wings to the fuselage was checked and found to be within acceptable limits. During this same alignment check, it was also determined that one main gear axle was set about one inch aft of the other, but its toe-in and camber were correct. The student and CFI then accumulated about five hours of instructional flight time in the aircraft after the alignment and toe-in check. It was the opinion of the owner that the aircraft was responding correctly to pilot inputs, but since it had both the standard "narrow" gear and a STOL (short takeoff and landing) kit installed, that it was just much more sensitive than the other tail wheel aircraft he had experience with. The FAA inspector who responded to the scene said that the aircraft had been damaged and repaired a number of times before, and that the realignment/warping of the fuselage due to these repairs had created a situation where the wing lift strut attach fitting adjustments where set to their limits (one at its retracted limit and one at its extended limit). It was his opinion that this realignment contributed to the sensitive nature in which the aircraft responded to pilot inputs. Except for the fuselage being out of alignment, the inspector did not find any other anomalies that he felt would have contributed to the sequence of events that lead to the accident.