On May 21, 1994, at 1030 central daylight time, a Piper PA-12, N7867H, sustained substantial damage during final approach to land on a private grass strip three miles east of Wausaukee, Wisconsin. The commercial pilot reported minor injuries, the one passenger aboard was seriously injured. The 14 CFR Part 91 flight originated from Shawano County Airport, Shawano, Wisconsin, without flight plan and operated in visual meteorological conditions. In a written statement provided to the NTSB, the pilot said that he was flying the airplane from the rear seat. After clearing the tree line on final approach, he placed the airplane into a slip to lose altitude. About twenty to thirty feet above the ground, turbulence inadvertently caused him to pull the control stick from its mounting place on the cabin floor. The airplane impacted the ground in a nose low attitude, bounced, and came to rest inverted. The pilot stated that due to the frequent removal of the rear control stick, he failed to secure the stick with the safety pin before flight. No preimpact mechanical malfunctions were reported by the pilot.