I was contemplating doing and iwagumi similar to this one a while back, with stacked sheets of sharp rock, if you can understand that.
Also, so happy you're using DHG and not somthing like HC or Glosso. I hope you stick with it untill it's a full carpet. There arn't nearly enough iwagumis that use DHG (that I've seen anyway).
SO BASICALLY, I hope you don't mind me living vicariously through your tank.
Wabi Kusa is just an Aquascape Katamari