The demand for an alternative to <sup>3</sup>He tubes in neutron detectors is growing. Specifically, the increase in challenging requirements for applications in research, industry, safety and homeland security triggered the search for better-suited detectors. Therefore, we developed a high performance, comparatively low-cost and easy to build cold neutron detector prototype (13.6 cm × 13.6 cm active area), employing digital silicon photomultipliers (SiPM) from Philips and a glass scintillator. The optical front end of the detector consists of a GS20 scintillator, enriched in <sup>6</sup>Li, a light guide, SiPM arrays and an aluminum cap. In order to find the optimal front-end design, a series of Geant4 simulations were performed. In this work, we present a comparison between simulation results and measured validation data, considering the average number of photons detected and the maximum ratio (brightest pixel response divided by the sum of all pixel responses), for multiple design configurations.