This paper addresses feedback design issues in ad hoc networks with simultaneous access of multiple users, when type II HARQ exploits a constrained capacity reverse channel. In such networks, communications performance is limited by interference and nodes operate in a distributed fashion; thus, efficient resource allocation relies on proper feedback signaling, which on the other hand can use only a limited amount of network resources. For this reason, we investigate how to determine a finite set of feedback messages, which accounts for the underlying type II HARQ error control and jointly regulates power allocation and medium access in an optimal manner.