As the world community, has become aware that exoplanets exist in abundance, it has inspired new observatories in search of Earth-like worlds. Technology development studies have highlighted the need for structures with extraordinary dimensional stability. Advanced materials such as silicon carbide and beryllium are costly and time consuming to manufacture. Using methods pioneered in carbon fiber composites, sandwich panels from silicon carbide and beryllium are proposed for lightweight, stiff, ultra-stable optical benches for instruments on new observatories such as LUVOIR and WFIRST. Assembled from flat stock and waterjet machined, the panels are extremely lightweight. A prototype panel is shown whose stiffness is a close match to the FEA. Fittings machined from Invar 39 for silicon carbide and AlBeMet for beryllium can be bonded to the panels to provide interfaces to optical mounts and optical components.