How deep is your sand bed going to be (if you're using one)? You want your rocks to be placed prior to the sand so burrowers don't wreak havoc on what you've created.
How wide is the tank? I have a 75g (48x18" footprint) which leaves a pretty narrow area to play with if you want space all the way around the rock work (I didn't want any rock laying against the back of the tank). To help mitigate this, drag the lines out at 30-45° angles toward the front of the glass; this will give the perception of depth where the really isn't much.
Is that really 55lbs of rock? The image below has roughly the same amount of rock and 3-6" of the rock is covered in sand. I'm not a fan of artificial bridges as suggested above but we all have our preferences so play around with a lot different options. I used .5" OD PVC to mock up my rock structure before I actually built and epoxied it together.