The Vespa community has asked us to stop calling it a "pet carrier", since the name conjures morbid images. So we'll call it a cargo bucket, that plastic bin that fits between the engine and under the seat of your Vespa.
The problem is that it has a sharp edge where it hangs on the body. This presses into the paint and causes micro-vibration that wears right down into the metal. Eventually it will create a rust ring the whole way around.
There's a product called "racer's tape", some call it "helicopter tape", but it is a polyurethane tape that is amazingly strong. It can be hard to cut with a pair of scissors if they are even slightly dull. I've used this for years on my Sunbeam Alpine where the hard top contacts the body of the car. This tape protects the paint and will not damage it even if you leave it on for years at a time.
