If you build a craft using a container controller and extensions (likewise ammo & harvest) be warned that the center of mass for loaded cargo is attributed to the controller, not spread across the assembly of extension as you might assume. If your ship or HV tips when you load it check where the controller is located. Keeping the controller near the center of mass when the containers are empty will minimize the impact of loading. This is the same thing that aircraft do- fuel tanks get located so that as they empty the CM for the plane doesn't shift in flight. Last image shows that this mass is assumed to be at a corner of the controller as opposed to in it's center ... it's pretty much impossible to get things exactly at the center unless you have an even number of blocks on each axis but perfect is the enemy of good enough in that regard. On HVs, for good yaw control make sure to locate the L/R engines behind the CM so that they have good leverage.
