The kobuki base by yourself won't drift, so it is sensible which the tilted inertia will cause the drift. Needless to say I'm able to hack my URDF having a weightless superstructure, but I needed to repair this in a more reasonable way. I tried all I'm able to think https://www.uk-exhibitionstands.co.uk/product/monolith-6m-display-wall-6x2-4/