Hello
The customizing from OMIR is only a "default value", that means, it is only considered when a material is extended to this storage location. If you change this setting and a material is already extended for this storage location, the setting won't be considered.
As I pointed on my first reply, you should change this setting directly on tab MRP4 of the material master. That way you can set only for the materials where it is necessary.
BR
Caetano