[Therion] Therion import of Survex Data

I am just getting to know Therion for the first time, because I am looking to create 3D models with surface overlays from my Survex survey data. I have managed to create a .lox file from a .3d file, but it does not include any passage walls. I just get a centreline. If I open my Survex generated .3d file directly in the .lox viewer it creates the walls from the LRUD data in the .3d file. But how do I get this data into a .lox model along with a surface? Footleg