Exporting from VW to Sketchup

[din]

I know it's a less than ideal workflow, but we've been trying to find a reliable way to export from VW (2009) into Sketchup

so that we can add materials and render etc (as we don't have Renderworks), and use Sketchup environmental plugins (such as IES). We are trying to ensure the VW windows and doors are retained as Sketchup components, and that other objects retain their VW classes as much as possible.

When I export as a DWG, the windows & doors come into Sketchup as components, but only the frame is visible - the mullions, transoms, door leaves and glazing are lost. When I have opened up the DWG in Autocad LT 2007, the mullion / transom / leaf geometry isn't visible, which suggests it's a VW export problem rather than a Sketchup import problem.

We've also tried exporting as a 3DS file (I know to combine coplanar faces to avoid triangulation), and all the geometry and surfaces come into Sketchup. However walls come in as a single group with the doors and windows within broken down into individual planes and lines which isn't that useful.

Finally we've also tried importing as an IFC via the IFC2SKP plug-in, but this time although all the walls and doors came in a components, some of the walls were missing.

I think the 3D DWG is the best approach, but is it possible (or advisable) to convert the windows and doors from VW plug-ins into 3D symbols before exporting, or is there a better method to export to Sketchup which retains all the window and door details?