The kobuki base alone would not drift, so it makes sense which the tilted inertia brings about the drift. Needless to say I can hack my URDF having a weightless superstructure, but I planned to resolve this in a more practical way. I tried all I can think of, and https://www.uk-exhibitionstands.co.uk/product/monolith-6m-display-wall-6x2-4-2/