The SU dwg/dxf exporter has what I would call a bug - it doesn't record the unit used in the exported file.
That means that most of the "receiving" applications interpret that the file uses inches. When importing to AutoCad, the application can be taught not to scale the import in any way, but I have found it easier to open it first separately and change the scale settings in the file before inserting it in my drawings.
For a DXF it would be possible to correct the file in a text editor, but it is still up to the receiving app if it reads the info correctly.
Anssi