Rockwork looks stable enough. That mined rock stacks well.
Reef Octopus makes a really good hang on skimmer. I've not seen one working, but the Eshopps hang on looks like a good design, as well.
My one piece of advice for new reefers... Nothing good in this hobby happens fast. Take your time, move slow, and enjoy the ride!
Welcome aboard, and good luck to you!