We extend an executable specification of a state-of-theart secure group communication subsystem to explore two dimensions of adaptability, namely security and synchrony under crash-recovery and intermittent connectivity scenarios. In particular, we relax the traditional requirement of virtual synchrony and propose various generic optimizations, while preserving essential security guarantees. In order to evaluate how practical and effective our generic optimizations are, we integrate the specification into ns2, bridging the gap between formal specification and classical network simulation.