Hi, I don't know if it is still needed. But the here published version was not satisfying me.
1. I had duplicate (or even triple) conversations with the same number and also single messages were missing. This was caused, because my N900 DB was holding different number formats. So I'm normalizing the phone numbers before I create the groups. (but only for german phone numbers)
2. The messages in the conversations were not correct sorted. I changed this by adding a sort to the select query.

Now its working for me If someone is interested in the .deb post here.