The virtual synchrony model for group communication has proven to be a powerful paradigm for building distributed applications. Implementations of virtual synchrony usually require the use of failure detectors and failure recovery protocols. In applications that require the use of a large number of groups, significant performance gains can be attained if these groups share the resources required to provide virtual synchrony. A service that maps user groups onto instances of a virtually synchronous implementation is called a Light-Weight Group Service. This paper proposes a new design for the Light-Weight Group protocols that enables the usage of this service in a transparent and dynamic manner. As a test case, the new design was implemented in the Horus system, although the underlying principles can be applied to other architectures as well. The paper also presents performance results from this implementation.