R12 - Sales Order Line Default

Can anyone confirm what controls what ship method defaults on the Sales Order Line when a user manually changes the lines ship to address?  We are having an issue where if a user changes the ship method on a line item to Next Day Air, the system is defaulting Ground upon the user changing the Ship To Account.

Is it the Attribute Defaulting Rules for Application Order Management - Entity Order Line - Attribute Ship Method that controls this?  We are currently using the seeded version.  The team definately wants the header to drive the default to the lines upon adding a line item.  But once the line item is saved, how can we control it so if the user changes the ship method on the line followed by the ship to that system does not default the ship method back to ground.