Fast neutron detection is important to the detection of illicit nuclear materials, and can help prevent those materials from being used or transported without discovery. Previous research has shown that Heavy Oxide Inorganic Scintillator crystals can be used to detect fast neutrons by capitalizing on their high inelastic scattering cross section. Composite scintillator designs combining crushed Gadolinium Ortho-silicate and plastic light guides have been proposed for enhanced fast neutron detection based on similar heavy inorganic crystals. In this thesis we have performed laboratory measurements and devised a Geant4 simulation of the ZEBRA design and several referenced detectors in order to characterize the neutron and photon detection abilities of ZEBRA detectors. We have validated the simulation and demonstrated its use to further optimize parameters for this promising detector technology.