I found this when I was looking for something else.
So, here:
My 3D modelling skills are rudimental. I made some shapes I can sort of moosh together with an off-the-shelf car model. Without all the finessing and filleting you might be able to imagine.
The one reproduces a similar boat tail on an older Beetle I did as part of a series:
The other is a maximal Kammback.