Radial SG force of the power law disc for different scale heights. The accuracy of our kernel increases with decreasing aspect ratios. Note that for ϖ ≃ 0.07 the relative error is beyond unity, which is a bias in the statistical measure due to a vanishing radial acceleration. We recall that in FargoCPT and Nirvana-iii we used a logarithmic and uniform radial grid, respectively.