I have a collection of tumblers in this style made by Carlo Tosi during the '60 (it was a wedding gift for my parents). They are so thin and light that you can bend them a little bit giving some pressure with the fingers on the sides... Now we have 30 pieces, but originally they where 36...
They are a classic here and many master glassmakers (Striulli, Fuin, Seguso) make them.
Cenedese is a pretty common name in Murano. Giovanni is a common name too.
I suppose that the signature was made by the artisan who decorated the glass, not by the glass blower; normally they are not the same person.