Congrats on the tank! I purchased the same one. It should have come with a thin foam piece that is the same size as the tank. My understanding is this can be placed under the tank to help with leveling. I do not think it is necessary though. As long as the plywood is level, you will be fine. As far as egg crate goes, I am new to saltwater, but have a lot of experience in freshwater where heavy rocks are used, and the main reason to use egg crate, is if there is the possibility of your aquascape collapsing. The SCA glass is very thick and if you do your aquascape correctly (don't have sand b/t your LR and glass bottom, don't just stack a bunch of rock loosely without it being stabilized and fixed in place) you should be fine. I know plenty of rock aquascapes that have been done without egg crate and without any problems. That being said, if you are going to have large pieces of rock, and do not trust yourself to not loose your grip on it while moving it around or rearranging, might be worth considering. The other downside (anybody else please chime in) is the possibility of the egg crate becoming exposed in the sand and trapping detritus which could lead to a nutrient problem in a reef tank.