Throughout the entire design process of any future military system, from function analysis through system operation testing, a key human factors question will be, "Will warfighters meet required performance criteria on demanding operational scenarios?" Although experimentation with real warfighters is essential, it may be too expensive to for all possible equipment and team design options. The Integrated Performance Modeling Environment (IPME) focuses on simulation of humans in complex environments and allows us to evaluate system concepts, designs, and team structures with simulation at a far lower cost than with real humans. For the Office of Naval Research Science & Technology Manning Affordability Initiative, the IPME was used to model human processes and human interactions with current consoles, as well as internal and external communications networks. The model is based on a demanding air defense warfare scenario containing in excess of 80 air tracks, 1160 scenario events and 150 human tasks. Modeled processes include air track detection and identification, escort, queries, warnings, and threat evaluation and mitigation. Some measures that can be provided by the model include the time to first identification, wait time associated with various tasks, and crewmember workload parameters. In parallel with model development, experimental data were collected aboard ship from eight intact crews using the same demanding operational scenario. This paper describes a multiple-step process in which the model is validated and calibrated, and discusses progress to date in this area. Then, the paper discusses how the project will modify the timing and function allocation rules in the model to allow experimentation with alternate team designs, automation and alternate human machine interfaces. This cycle of model validation and model-based design evaluation provides a powerful way to integrate human factors engineering into the design of future systems.