The Slic3r preview shows a bit more detail:
Even an inch-thick handle wouldn’t have enough mojo for the task.
Wikipedia has the equations you need to go from the easily measured “height” (vertex to opposite side) dimension to the pentagon’s “outside radius”, which equals the radius of the circumscribed circle needed by OpenSCAD.
The OpenSCAD source code as a GitHub Gist:
Sorry ’bout that … had to do it.