No one middleware communication model completely solves the problem of ensuring schedulability in every DRE system. Furthermore, there have been few studies to date of the trade-offs between alternative middleware communication models under different application scenarios. This paper makes three contributions to the state of the art in middleware for distributed real-time and embedded systems. First, it describes what we believe is the first example of integrating release guards directly with CORBA distributable threads to ensure appropriate release times for sub-tasks along an end-to-end computation. Second, it presents empirical results in which release guards improve schedulability of distributable threads compared to a greedy protocol in which arriving tasks simply begin to run as soon as they can. Third, we offer the first empirical comparisons of the distributable thread and event channel models under three different communication scenarios and then using a randomized workload.