In this paper, we do performance analysis of the cooperative HARQ protocol in a wireless adhoc multihop network employing spatial ALOHA. We model the nodes in such a network by a homogeneous 2-D Poisson point process. We study the tradeoff between the transport capacity submetrics inherent in the network when using cooperative HARQ protocol and opportunistic routing by optimizing the transport capacity w.r.t the network design parameters, coding rate and medium access probability. Using approximations, we obtain an analytic expression for the expected progress of opportunistic routing. By way of numerical results, we show that the network design parameters obtained by optimizing the analytic expression of transport capacity closely follows that of Monte Carlo based exact transport capacity optimization.