I don't like square plates on EP3s, especially on the front, the number plate recess is just far too obvious.
I've always used trim tape to stick my number plates on, I've never had a problem. Just make sure you prepare the surfaces before sticking it on. The bond is very good, you couldn't pull it off without breaking the plate. I used fishing line to get an old one off in one piece, took several mins, no longer than it would take someone to unscrew one... I personally don't believe theft is an issue.