Hi @nofussrussell ,
Are you able to import into ArcGIS, but the data just comes in at the wrong place? I don’t use ArcGIS, but in QGIS, you can set the coordinate reference system (CRS) of an imported layer in it’s properties after you import. I’m guessing your exports from Rhino have no CRS set.
To help with more detail, please post some example files that illustrate your issue.
-Brian