To address the intense heat and electromagnetic loads that can occur during a disruption, a shattered pellet injection (SPI) system will be utilized by ITER. Along with experiments in present devices, accurate modelling of the plasma response to a SPI system and validation with present experiments is required to make predictions for ITER. 3D MHD models are beneficial for better understanding of the radiation characteristics, MHD activity and other 3D phenomenon. In tandem with 3D simulations, reduced models can be utilized to carry out large parametric scans to understand the role of key SPI parameters and validate their relationship with relevant disruption mitigation metrics. We use the 1.5D disruption simulator code INDEX to validate the trends in penetration and material assimilation observed in the ASDEX Upgrade (AUG) tokamak with focus on three key SPI parameters: fragment sizes, speeds and pellet composition. Results from mixed neon-deuterium pellets as well as pure deuterium pellets are presented along with quantitative comparisons with experimental measurements. Larger and faster fragments are advantageous for improving material penetration and assimilation, however faster fragments are also expected to lead to a quicker thermal quench (TQ) onset. While neon assimilation increases with injected neon amount for low neon content injections (<5%), it saturates for higher neon content. Material assimilation for pure deuterium injections in the simulations is found to be similar to line-integrated measurements in the AUG experiments a few milliseconds after the fragment arrival. In addition to AUG based studies, results of material assimilation for pure deuterium injections in JET are also presented. Simulations indicate that the material assimilation is initially limited to the plasma edge due to the plasmoid drift and the core density only increases on longer timescales. Simulation efforts planned in the near future are also discussed to gather feedback from the participants.