There is a new polygon wireframe to 3dm converter now available here:
http://moi3d.com/download/Obj23dmWireframe.zip

This enables bringing polygon data into MoI to use as construction guides.

Unzip it to some folder, and then you can run the Obj23dmWireframe.exe program.

It will prompt you for the name of an OBJ file, and after that the name of a 3DM file. It will read all the polygon data from the OBJ file and convert the edges of polygons into line segments, and save those line segments to the 3DM file that you specified. You can then load that 3DM file into MoI and use those line segments to snap on to.

- Michael