We develop a hybrid approach for computing the system-level imaging performance of THz focal plane arrays (FPAs). We use the full-wave moment method to analyze the performance of THz FPA antennas. Antenna topology is optimized for impedance matching with the integrated THz sensors and pattern matching to external optical components. The effects of the quasi-optical lens train are accounted for using the paraxial wave approximation. Here, we consider a simple reverse microscope configuration using a THz FPA situated conformally behind an extended-hemispherical silicon lens. In order to properly form the image, an objective lens is also used. Here, we demonstrate the system-level THz imaging performance of the reverse microscope THz FPA camera using the hybrid fullwave/paraxial-propagation approach.