Record yourself. Listen for the "gap." If you hear a silent gap between the two notes of the portamento, you are stopping your breath. This is the #1 error in Lesson 11.
Let’s look at what you will encounter on of a typical mezzo-soprano Vaccai book. vaccai mezzo soprano pdf 11
The leap C (do) to B♭ (te) is an ascending . Vaccai instructs: Record yourself
For a mezzo-soprano, the passaggio usually occurs around E-flat or E-natural above middle C (first bridge) and again around E-natural or F-natural an octave above (second bridge). vaccai mezzo soprano pdf 11