In order to maximize throughput in end-system multicast, it is necessary to have fine-grained control over the transmit load of each participating member. This both avoids bottlenecks where members are overloaded, and allows heterogeneous members to contribute as much transmit capacity as they are able or willing to. In this paper, we describe and simulate an unstructured endsystem multicast protocol called Chunkyspread that provides members with fine-grained control over their transmit load, scales well, has relatively low latencies, and can tolerate high membership churn. Chunkyspread is designed as a flexible framework that easily incorporates different constraints and optimizations. For instance, it is straightforward to add tit-for-tat or path disjointness as constraints to the system. This paper demonstrates the performance of Chunkyspread through extensive simulations, and provides partial validation of these simulations on Emulab. It also provides detailed comparisons with Splitstream, a structured heterogeneous end-system multicast protocol. The simulations show that Chunkyspread provides far better control over transmit load than Splitstream, while exhibiting comparable or better latency and responsiveness to churn.