Regarding the chart in post #60, the average (or mean) surface current may have little significance in calculating the path of floating debris. If the currents shift significantly about the mean on a seasonal basis, a northerly current in the area and time of the crash could push objects into the westerly stream at 12-15 degrees South latitude.
Also, it isn't clear from observation of these photos what orientation this flap would float (some analysis of sea life attachment might give clues). If it floated higher in the water for a significant period of time, its surface exposed to winds might have a significant effect on its drifting course.
