We have previously introduced the notion of arguing from experience, whereby agents debate a classification problem using arguments based on association rules mined “on the fly” from their individual datasets. In this paper we extend PISA, which allows for n agents to argue about cases which have n possible classifications. By allowing any number of agents to participate all the agents supporting a given classification can form a collaborative group for the purposes of the dialogue. We describe how the system is organised, give an example, and report results which suggest that allowing groups in this way has a beneficial effect on the quality of the result.