sorry man, I couldnt get it working... i already start modeling in the poly mode, then convert to the mesh. Triangulation is something that i have added later.
[by the way: Do you believe that it can be skipped? (I am not sure of triangulation since it increases the poly count, but gets rid of some sharp triangles(gives you control over the how those triangles are produced..)]

I did extrude the edges and exported as 3ds but after importing to the med and merging the vertices, still, the same problem persists. And I dont see how this method will improve the wrong shading of the smooth surfaces. When I export as obj it seems that the vertices weld (the model is closed) but the smoothing groups are messed up (I am checking this with another program (deep exploration)since I alsın coulnt import those objs into med there seems to be problem with the normals...) but still no results for me thanks for trying though. Would you mind sending your working obj or 3ds files to me? Maybe it will show me what i am missing..