We describe ongoing work in adding congestion control extensions to an existing negative acknowledgement (NACK) oriented reliable multicast protocol. Our previous work adopted and used the concept of a dynamic worst path representative (WPR) receiver for equation-based rate adaptation at the multicast source. We have further refined this approach. We present a design overview and simulation results of these extensions within a working reliable multicast protocol (MDP-CC, multicast dissemination protocol congestion control). Our analysis of interflow fairness with steady state TCP unicast sessions demonstrates friendly behavior across a set of scenarios. Testing with more dynamic TCP flows and more complex topologies demonstrates the WPR approach adapts well to changing congestion conditions.