In the latest project in which I am involved, I am having to import data from Survex (actually from Compass via Survex but that's another story!). This requires importing survex 3d files. The problem that I have is that .3d files generated in the most recent iterations of Survex cannot be read by Therion. I had the same problem some years back & eventually they caught up with each other, but it seems that the Survex format has changed too much once again.