Here's two diagrams from the paper. Notchback with and without small rear spoiler ("kick-up").
Note that with spoiler there is a:
- major pressure increase on boot / trunk lid
- major reduction in suction peak due to clean separation
- small reduction in drag and larger reduction in rear lift
In one sense none of this is startling - the pressures are what you can measure yourself on cars that have attached flow on the trunk / boot. But at the same time it's good to see such clear evidence of the changes possible.