Allegro in G major

This is a mysterious and fragmented piece from the pen of a young Mozart, the only source being the famous portrait by S. dalla Rosa of Wolfgang as a 14 year old, painted whilst he was staying with his father in Verona, Italy.
It is a merry piece, as one might expect from Mozart, originally intended for the harpsichord, but it works very well on the organ. Unfortunately it's only a fragment, so one has to improvise a little to bring the piece to a satisfactory conclusion. I wonder how long the original actually was...
I decided to play it on the fine baroque Cyriac Werner organ of Strassburg, Austria via Hauptwerk.
The registration is

Positiv:
Gedeckt 8'

Hauptwerk:
Gedackt 8'
Ocktave 2'

Pos-Haupt.