A German friend of mine who also flies N-reg is a member of AOPA Germany. He says they are a reasonably well connected group and do a lot of good for private aviation in Germany.
If you ever want to convert to a german license and need a level 6 certificate for English Language Proficiency, the AOPA Germany seminars and exam sessions are very good.
But instead of asking on a forum, why don't you give them a call ?