Hey NigeC,
Do we talk about Vray4trueSpace here? That’s too long ago, sorry. I have no idea. I haven’t installed tS anymore since years. But i remember that trueSpace had explicit DirectX and VRay materials. And this means the materials are probably saved in the rsscn or a mtl file. The Vray version for trueSpace was a special version too.
Sorry that i cannot be of bigger help here.