If you have the .bin file for the child object in the same folder as the stock item then there's no need to have other Provider/Product boxes ticked, the .Geo still needs to be outside of the parent item's folder tree though.
Many scenarios use at least one item from the default Kuju tree, so having a Kuju/RailSimulater/ChildObjects folder for additions such as this further negates the need for additional P/P box ticking.
