I said it will be easier now, because we have an improved micro-exporter which retains the coordinates from TG2 in the model + a wireframe preview which allows much easier tweaking of positioning your model.
About the improved exporter: as you may know TG2's coordinate system is the most accurate near the 0,0,0 coordinates. So if you export something from TG2 then try to have your region of interest at or nearby the 0,0,0 coordinates.
For this you can use a transform shader as final shader before the planet and move the whole scene to the correct position, then export, do your ivy thing, re-import, match position of ivy with terrain and correct for the transform shaders input.
For example, if you had to move your terrain + 1000m on X-axis to get your region of interest @ 0,0,0 then after matching your ivy with you terrain you remove/disconnect the transform shader to your planet and set the ivy's position to -1000m.
I only used a small sphere WITHIN the scene as a reference point in ivy generator, because all of the above possibilities weren't available then.
In ivy generator I let the ivy start growing onto that tiny sphere from where it grew on my terrain.
By doing that I knew that the starting root of my ivy needed to be at the same position as my sphere.
So I only used it as a reference and did not put my entire scene in a sphere
