The kobuki base by itself will not drift, so it makes sense that the tilted inertia leads to the drift. Of course I'm able to hack my URDF using a weightless superstructure, but I wished to fix this in a more sensible way. I tried all I'm able to give https://www.uk-exhibitionstands.co.uk/product/pop-up-stand-3-x-3-bundle-curved/