Alright.  So here is my first draft of what I want to do with my 90 gallon.  I am not showing the egg crate as I don't know how to make it in the program.  I am wondering about the sand bed, though, because in my current tank the sand in the front of the tank is constantly blown away from the glass, so this design could pose a problem.  Especially, in the somewhat high flow I want to have in the upper portion of the tank.  So I don't know yet.