Hi Bob - so an STL file is a very basic file format, it only contains a big list of triangles in it with every triangle specified by x,y,z coordinates, there is not any way in it to control edge visibility.

MoI does also have a direct SketchUp SKP format export, is there any particular reason why you're using STL instead of the direct SKP export?

There is a way to control edge visibility in SKP, and MoI uses it to turn off polygon edges for polygons that were on the interior parts of a surface and leaving only polygon edges that were along edges in the NURBS model to be showing, it does not pay attention to whether those edges were hidden or not but there will be a whole lot less visible edges to mess around with probably.

- Michael