Rearrange your entire setup,...
From the couple picture you have I would do couple things a little different,...keeping in mind you want chalice SPS and clams to fit just perfect and maybe some Euphyllia corals later,..
You have few different sizes of shelf Some really nice Pukani and Premium Fiji I believe.
I would place the smallest Fiji in the middle bottom then place one or maybe 2 shelves over top and only going no more than couple inches of the bottom pane enough hiding and swimming for smaller fish.
I would upright the pukani in a cone shape over half the tank center going back almost the entire length,back laping them and enough space for the fish..Greg some more Fiji leaning towards the back pane creating tunnels and flat surface for more smaller pukani rock and build it all on a similar disign and in between have a couple more smaller shelves petruding outwards for chalices or SPS as now you have an almost 3D look as your front is semi full with the 1st shelves you placed and perfect for the clams or Euphyllia corals.
Your entire top of the rocks and all crevices in the Pukani is perfect for all your SPS.
YOU DON'T Need to use those beautiful pieces of shelf as covering for the overflow.
That's only one design in mind.
Another design as I call it mountain to ravine with a far hill.
Starting from the overflow box with again few smaller pieces of Fiji placed on the bottom then on top going length wise of the tank place the longest shelf petruding away.
Then build the biggest mountain style going centre of the tank with Pukani leaving the back overflow wall to be filled with Premium Fiji covering it entirely keeping in mind not too dense but backwards overlapping (keeping the 3D effect in mind)
Now you have the entire 3/4 of the tank to fill maybe one or 2 freee standing and almost the entire height on the tank with maybe smaller shelves in between or maybe grab a pukani and mold it to a hammer or an L shape piece ,...
I hope you don't mind my imput on your design as it is nice but with what you bought from me you could make it the craziest look lots of people only dream of,...