In order to create spring designs with a specific unit system, it is necessary to open (File : Open menu item) a design entry that has been pre-configured for that unit system.
Each ODOP design type will always have a system provided default design starting point (named "Startup") available. The Startup design for each spring design type (compression, extension & torsion) utilizes US customary (inch, pound) units. In order to create a design utilizing metric units, simply open the "Startup_Metric" entry.
It is possibile to personalize the default Startup design. See: Default Designs for more information.