18% sounds like it's the old Inkscape DPI issue. Basically Inkscape runs SVG at 90dpi while other editors, like Illustrator run at 72dpi. Not sure what Pawaga used to make that file and I also can't find the Ponoko forum posts I read about it. Try this;
Get and open Ponoko's P3 inkscape template.
Open Pawaga's file
Copy and paste the contents over to the P3 template.
The p3 template has settings in it that should correct the sizing issue.