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I dont have a tank as big as yours, but i think a sheet of Styrofoam is normal on larger tanks. I just use foam drawer liners, they seem to work fine for me on smaller tanks.
I saw a King of DIY video a few years back, where a tiny imperfection on the top of the stand caused the base of his tank to crack in the middle of the night. 100g of water on the floor. A mat would have prevented this. Of course it may never happen, but better safe than sorry.