This paper details both theoretical and experimental results of an enhanced model to design MgF2/ZnS double-layer antireflection coatings for AlGaAs/GaAs heteroface solar cells. The main contribution of this work is that a method for taking technological tolerances or uncertainties into account in the optically relevant parameters for antireflection coating design is presented. This is done by the calculation of contours of quasi-optimum performance for a certain range of variation of the uncertain parameters. A number of experiments testing different aspects of the predictions made by the model are commented on, showing good agreement with the calculated performance. Unwanted window oxidation, described in Part I of this work, has proven to be the key factor influencing quasi-optimum contours.