Thanks for your effort
I only have one obsevation this conversion, The edges of the models is blurred and it seems that there’s a fillet in all corner, I love fillets but in some cases I don’t need it like in this case
I also hope to change the material per face in sketchup eg, the interior face would be Wood, and the exterior would be Steel
Since you send your model from Rhino to SketchUp as a single polysurface, it arrives to SketchUp as single mesh, so it is quite hard to distinguish faces as you said. What I can suggest is to split your faces that you want to assign different materials in Rhino into different polysurfaces before send to SketchUp. This should be quick win for you.