Elastic plastic self-consistent (EPSC) simulations are used to model synchrotron x-ray diffraction observations from deformation experiments on fayalite olivine using the deformation DIA apparatus. Consistent with results from other in-situ diffraction studies of monomineralic polycrystals, the results show substantial variations in stress levels between grain populations. Rather than averaging the lattice reflection stresses or choosing a single reflection to determine the macroscopic stress supported by the specimen, an EPSC simulation is used to forward model diffraction data and determine a macroscopic stress that is consistent with lattice strains of all measured diffraction lines. The EPSC simulation presented here include kink band formation among the plastic deformation mechanisms in the simulation. The inclusion of kinkband formation is critical to the success of the models. This study demonstrates the importance of kinkband formation as an accommodation mechanism during plastic deformation of olivine as well as the utility of using EPSC models to interpret diffraction from in-situ deformation experiments.