Hello -
I start with this image :
Then I look at a side view of my wagon and see that the maximum height *appears* to be above the rear seats :
That led me to this overlay, where the dark line of the tear drop shape is scaled to be "above" the outline of my car :
If I were to limit the extension of a "Kamm-Spoiler" to the rear bumper, that would imply a ~7 degree slope that would take me to this :
Does this look correct?
CarloSW2