This paper aims at presenting a formal modeling and verification method of a cross-layer technique to building an efficient P2P unstructured overlay over MANET underlays. Peer-to-Peer (P2P) overlays are formed dynamically to create a virtual network on top of an underlying physical network such as the Internet. P2P overlay networks can also be deployed over Mobile Ad hoc Networks (MANET) to address content discovery issues. However, deploying P2P systems straight over MANET do not exhibit satisfactory performance. Bandwidth limitation, limited resources and node mobility are some of the key constraints. The rational behind our proposal is to take advantage of MANET underlay to select and maintain physically nearest and fresh P2P neighbors. The combination of elementary strategies makes our overlay building likely- matches the MANET underlay, thereby, leading to efficient paths between P2P neighbors and reduction of network overhead. The formal modeling consists in capturing the behavior of wireless nodes and the medium using the input language of the UPPAAL model checker, that is a network of communicating timed automata. Last, we proceed with the checking of some safety and liveness properties by means of this tool, such as deadlock-freedom.