I just found this thread and just want to say you are off to a great start! I am pursuing and similar 'Iwagumi on a medium sized budget', and this has given me some inspiration. I have the same tank and light and am working on getting my substrate. I will be starting a journal in the next few weeks. I will be using Aquasoil and some HC and Crypts. It's good to see more people working with this tank, as I think it can make a stunning setup.
Keep up the good work and I look forward to seeing updates! Oh, and one comment: I think sloping the gravel more from front to back would look better.