The kobuki base by yourself would not drift, so it makes sense the tilted inertia will cause the drift. Obviously I can hack my URDF by using a weightless superstructure, but I needed to deal with this in a far more real looking way. I tried all I'm able to https://www.uk-exhibitionstands.co.uk/product/air-inflatable-backlit-circular-tower-2m-2280mm-h/