looks like the UG is going to good hands!
the hardscape looks great. The only thing you might want to try is if you have some more aquasoil, add some to the where the large grouping of stones are. The rocks look a little small in there which was my problem when I tried a iwagumi in a 10gallon. I steeper slope will make the rocks look bigger and put them closer to the surface of the tank.
I see you are trying without co2. I started with only excel and the UG just seemed to do okay. The color was real pale green and looked a little scraggly. Once I threw on a DIY co2, it exploded.
Best of luck with the project!