OK after looking over what I wanted to do I had to lower the sub-floor by 1 inch or less (remove 2 square rows from egg crate). I wanted to make sure the substrate does not slide out the front door LOL. This will also make it easier to line the out side edge around the false floor with stone. I also used black GE silicone II to cover the back of the vivarium. Some say this helps with the Great Stuff sticking to the glass, some say it does not matter. I did it so the back of the tank from the outside has a finish look. Will post Pics...