Well - we have couple of people here , and maybe there will be some more. We all know that there are cheap d-bahn ticket that covers wide area:
I was never in Bremen , meeting(s) does not need to be in Hamburg. Let's see if someone more will be willing to join. We can start to plan free day one weekend in let's say September (?); for first time 3-4 people is enough - breaking the ice is always hard ...