Most of the people I know who deal with autocad file submissions from the
outside actually prefer not to accept DWG files because they never quite
feel confident that what appears the other end will match what was saved.
Mind you with DXF having a 600 dpi tiff of the drawing as a check
reference is a good idea as well. I've had funnies between qcad and
autocad where things like linesizes changed mysteriously or extra bits