\defaultfontfeatures[PennstanderMath-ExtraBold]
{
  UprightFont  = PennstanderMath-ExtraBold.otf,
  BoldFont     = PennstanderMath-Black.otf,
  %script-font  = PennstanderMath-ExtraBold-script.otf,
  %sscript-font = PennstanderMath-ExtraBold-sscript.otf
}