As I wrote you by email, there is a big problem if you consider COMUNI as ADM3. In fact now in Italy and either in Spain we have 2 geonamesid for the same place: one for PPL another for ADM3. Actually it lead to unstalbility of geonamesid because user assigned to PPL geonamesid cannot be related to their ADM3 geonmaesid.
This fact vanish all my effort to map user by geonamesid, because at the end of the tree we have no stable leaves.