MATLAB code that generates all figures in [Almquist and Dunham, 2020, https://doi.org/10.1016/j.jcp.2020.109294 ]. The paper considers narrow-stencil summation-by-parts finite difference methods and derives new penalty terms for boundary and interface conditions. The new penalty terms are significantly less stiff than the previous state-of-the-art method on curvilinear grids. On highly skewed grids, there may be an order of magnitude or more difference in the time-step restriction.