I don't know about clear coating over the tape. I would check with a paint shop or a shop that sells automotive paints. It may be that there is a reflective paint which would allow you to mask things off in a pattern that pleases you.
I see you share my affection for the Karmann Ghias.
If you are approaching this as a fun project, it should be a great success. It is just that the bug platform is difficult to turn into an aerodynamic affair.
I am sure you have seen pictures of the
VW XL1 Project, but here is a link to some things about it. They have been doing a lot of thinking about how to make things more efficient, especially the aero part where there are great gains to be achieved. Here are some more
images.
Cheers