In a recent paper we introduced a method for proving conservativity of logical extensions using logical translations. The idea of this presentation is to show various applications of this method to fibred logics. Among these, we include an alternative proof of conservativity for the fusion of non-trivial modal logics, which generalizes also to a wide class of sub-classically based modal logics. A nice aspect of this method is that it is purely syntactic, contrasting with existing proofs for similar results that strongly use semantic reasoning.