The Kobuki base by itself isn't going to drift, so it is sensible that the tilted inertia will cause the drift. Not surprisingly I can hack my URDF with a weightless superstructure, but I needed to resolve this in a far more real looking way. I attempted all I'm able https://www.uk-exhibitionstands.co.uk/product-category/light-box-displays/casonara-blimp/