I drove like 4 years without any licenceplate, simply because it's ugly.
Lucky me, the cops never caught me ...
but the last years I did it with tape.
I don't care because I removed it directly when I came to a place or meeting.
Now I'm using T-bars, so I use the simple solution like Andi, and it works !!!
On the highway nobody is watching how you mount your licenceplate, so if I were you just do it as easy as possible.