[Therion] Surface Contours

I have randomly distributed surface points from a Post Processed Kinematic GPS survey (accuracy ~10cm) and wish to calculate surface contours. The reason for doing this is to have detailed data for all the shakeholes. Would like to import the contours into Survex/Therion so these can be seen above the cave. Has anyone else done this and how ? My current thinking is to use the QGIS Contour tool to generate the contours and then import these into Survex/Therion as elevation strings using some intermediate data format yet to be decided. Thanks, Kevin