Setting "Default Line Cap" via iPlot / PW Renditions

All,

    I need to change the "Default Line Cap" setting to "Flat" but I can't seem to find any way to do in iPlot / Renditions.  We use .set and .dscript files with iPlot, but after looking through the documentation, I cannot find a setting or means to set this value.

I can see the setting when printing directly through MSCE inside the .pltcfg file under Base Properties > General > Default Line Cap. 

Thanks in advance.