The structures of NinAlp clusters of all compositions with n+p=12, 13, and 14 are studied both experimentally and theoretically. Experimental reactions of the clusters with N-2 are used to determine the number of Ni atoms residing in the cluster surfaces. In agreement with the theoretical predictions, the N-2 saturation levels are consistent with clusters having icosahedral and icosahedral-based structures. The various N-2 adsorption channels seen in the experiment are explained in terms of the computed composition-dependent patterns of the configurational energies of the different structural forms.