Marc,
Here is a link with a good description of what is required for making modifications to Experimental aircraft in the US.
http://www.ruleaviation.com/experime...operating_.htm
I know Germany has very restrictive laws. Just as an example a friend from Germany told me it requires a special permit to change to an aftermarket brake line on his motorcycle.
Where in Germany are you? I took a ride in a private plane of a business acquaintance from Mosbach Airport. We flew over the company's plant in Pfedelbach, and over Heilbronn and Heidelberg.
Dave