"There is some confusion whether the rear license plate must be a big one for cars or a small one for motorbikes.
My registration office insisted on a small one!?

Can I get into trouble if I am traveling abroad with only a rear license plate?"

As a german, i have no front license plate, and as far as I know, for those questions, it is the law of your home country, which is what you have to do or not to do, so no problems. I carry a helmet with me, I prefer this on the Autobahn, especially when it is raining. I made 30.000 km in Germany, France, Netherlands, Belgium, Switzerland and UK, never had any discussions with the police. And I wear sailing clothes when it rains, perfect for me (and a good suncream (!))

Achim alias Waldemar