Quick question where is your overflow (corner, or middle and sticks out into the tank), just curious that it doesn't protrude into the tank?
The picture that I am seeing has the overflow box sticking out in the middle protruding from the back wall. If this is the case, then unfortunately both of your Rock examples will not work.
Plus your rock work is to close to the glass on the sides. You will end up kicking yourself in the end due to flow restrictions and being able to clean your glass.