I do the tapping on the back side with the goal to put the back under tension to balance the string tension , even if I know Stradivari was doing the tapping on the top side. here are the pics of the Reynier Stradivari 1727 showing the mark left visible.
It’s a Bois d’Harmonie rosewood tail piece. I have tried to tune the after length to a fifth but I have not seen any better sound with that. So I keep it short.
Visually, Montagnana, Busan etc look completely different from the cremonese , a bit more like Andrea Amati.
pietro Guarneri is an exception, completely Cremona look.