The kobuki base by itself will not drift, so it is sensible the tilted inertia will cause the drift. Not surprisingly I am able to hack my URDF by using a weightless superstructure, but I planned to fix this in a far more practical way. I tried all I can https://www.uk-exhibitionstands.co.uk/product/air-inflatable-backlit-square-tower-3m-3200mm-h/