This paper presents a new strategy to form P2P IP Telephony overlay for wireless ad-hoc networks. In the proposed strategy a structured P2P system is considered where some nodes, called super-nodes, with higher capacity form the overlay and provide registry and call routing services. As selection and admission of new super-nodes in wireless ad-hoc networks is more challenging than backbone networks, we define the strategies to select and admit new super-nodes into the overlay. On one hand, scarce resources and fluctuating link quality demand additional criteria than just node computing resources for super-nodes selection. On the other hand, the indiscriminate increase in super-node number can raise the call session setup delay and degrade the quality. This is due to the relaying of packets across multiple wireless links. In this paper, we first define the criteria to select super-nodes and then the major part of the paper is dedicated to defining the required strategies to admit new super-nodes. Our admission strategies add new super-nodes to the system whenever they are required. Since the strategy does not simply admit all eligible super-node candidates, this ensures control over the number of super-nodes and keeps the session setup delay within to the required service level threshold. We define a queuing network to model our system and evaluate the efficacy of our admission strategies with intensive simulations. Furthermore, we have implemented a P2P IP Telephony system that operates on wireless ad-hoc networks and validated the performance of our admission strategies on this real platform.