Recent detailed simulations of void growth and coalescence leading to spall have demonstrated that inertial contributions from rapid void growth can substantially modify the stress pulse that travels to the free surface and the associated free surface velocity measurement. There are significant consequences in that the spall stress inferred from velocimetry can differ appreciably from the peak stress at the spall plane for high loading pressures. In this work, additional large-scale, direct numerical simulations of void growth and coalescence are conducted to quantify the inertial effects on inferred spall stress. The calculations examine dependencies on loading pressure and release rate as well as the size and volume fraction of void nucleating particles. The results also address long standing discrepancies in inferred spall strength between loading profiles with an abrupt release and a ramp release.