Roll feed in postscript custom paper option blanked out?

Sure wish I could use the roll feed radio button instead of breaking up longer sheets by the 100 inch max constraint in the postscript custom page size definition menu… Instead it appears to be inactive despite being present.

Is this a me thing or should it somehow work?

Wish I could actually save these custom page sizes for later use too…

Thanks!

    • Dave
      rhino v5 via bootcamp