Here is the root system on H. praetorii after 12 weeks in semi-hydro using Grow Stones.  I think it is a pretty impressive root system for that amount of time.  I will however give you a warning about shipping rooted plants in Grow Stones – Don’t do it.  I recently shipped a plant a little smaller than this one to a Hoya friend, and the Grow Stones were so rough that it acted like sandpaper and rubbed the cambium layer right off the stem.  It essentially cut the root system off from the rest of the plant.

Grow Stones are Good for Growing, But not for Shipping!