I removed my plenum after i noticed everything in my tank was sinking because the sand was too small and slowly going through the screen so i had to redo my tank. Top picture is the old aquascaping bottom is the new job. Opinions plz!
I'd try to go a little more vertical man. Space those rocks out as much as you can and do lots of caves. Caves are cool. If your'e worried about structure, use a bit of plumbers epoxy to make a good fit between rocks.
This post has a pic of my aquascaping. Tanks is only 4 mo old though.
There are a lot of tanks with stacking rock and the steep side of many reefs this emulates. It also allows frags to sit up close to the light. The best design is to find a prototype photo or dive location and try to duplicate it. Hiding the overflow box sounds like a good idea. Leaving more swim space with lots of caves and a lower left or center gulley for your fish could help with small schools, another natural aspect of the design.
In the end, what looks best to you and causes you to spend hours observing, is the best personal choice.
Nate I am going thur a little bit of the same of ideas for my aquascape. But with live rock is it ok to use epoxy? I want as many caves as possible and I have to admit I scratched my tank with falling rocks but what is the best way to build my aqua scene?