A design study for the γ-ray detector array of the gSPEC project, which aims at measuring nuclear moments at GSI/FAIR, is presented. Foreseen setups, involving DEGAS and the new gDEGAS triple cluster detectors for γ-ray spectroscopy are simulated using the Geant4 framework. The main characteristics associated to these detector assemblies with the envisaged configurations, namely the photo-peak efficiency and the angular resolution, are discussed. A new correction procedure for a better reconstruction of the time-perturbed angular distribution is proposed.