Hi Joy:
I have also been working on our family tree for several years, having ancestors in the Alessandria region of Italy. Although the "Ivaldi" name is very common in Italy, what interests me about your posting is the combination of Ivaldi/Tassistro in your family tree.
I happen to have the same combination present in the form of my paternal great-great-great grandparents:
GIOANNI IVALDI married to ANNA MARIA TASSISTRO
around 1830's in the small town of Cassine, located between Genoa and Alessandria, in the province of Alessandria, Italy.
I don't know if my Ivadis were original from this town or imported in the form of my paternal great-grandmother who's name was Maria Giuseppina Ivaldi (Gioanni and Anna Maria were her grandparents). Her parents were: FRANCESCO IVALDI and LUIGIA (ANGELA) BADANO.
I have been working on my maiden name's family tree: PREDAZZI and the IVALDI name is a common combination dating back to the late 1700's.
I would appreciate any sibling information you may have on the Ivaldi's or Tassistro's.
Monica Predazzi