Nope, not me... I don't have a Greenstalk.I think maybe it was @Sally PB who made it for her Greenstalk?
I do make my own potting soil, though. I use 80-100 pots' worth of soil, and the pots are the size of large cottage cheese/yogurt containers, so that I don't have to up-pot anything. That's a lot of potting soil!