Stiff, ultra-lightweight thermal-formed polyimide panels considered here are examples of next generation gossamer structures that resolve some of the technology barriers of previous, membrane-dominated gossamer designs while maintaining their low mass and low stowage volume characteristics. The research involved dynamically characterizing and modeling several of these panels to develop validated computer models which can be used to determine the effects of changing manufacturing parameters and scalability. Modal testing extracted the first four structural natural frequencies, the first occurring at 71.9 Hz. These data were replicated by simple, coarsely-meshed shell element finite element models that are significantly smaller than previous finite element models of similar structures. Overall, the research contributes to the total knowledge base of gossamer technologies, advances stiff panel-based structures toward space qualification, and demonstrates their potential for use in apertures and other spacecraft.