The original source for this piece (Leopold's transcription of his son's sketch) does not reflect either edition you have. The bass note on the downbeat is doubled at the octave, but the G is not. This remains consistent throughout the movement, and from a musical standpoint, makes a lot more sense. It is the metrical strong point - the 3rd beat is not considering the piece is "felt" in 2. There is actually no forte marking at the beginning of the manuscript either, but it is assumed based on later passages.Good luck - it's a great piece.- Andrew
Do you know if Mozart's keyboard went down to that low G?