I occasionally use egg crate (light diffuser) inside the aquarium to buffer the bottom from falling rocks, although I do not think I’ve ever had a situation where it actually protected the tank from damage (I feel it is a complete overkill protection, although overkill isn’t a bad thing)…
I’ve never used Styrofoam under a tank until recently. For many years I set the aquariums directly on the manufactured stand or the home made stand (I’ve made many of my own stands)…
I recently bought some used tanks that are ‘frameless’ sp the entire bottom pane of glass sits on the stand. In this situation I chose to use foam on top of plywood (for a fuller support) on top of the 2x4 stand…
Tanks blowing out is very uncommon, but not unheard of. But I highly suspect that almost every time a tank blows out, with proper analyzation we could identify the ‘user error’ that cased it…
…and I don’t mean any offense by this as I’ve had tanks blow out and I have identified my own user error…
I do not feel that using egg crate between the tank and stand would offer any benefits and would bring some liabilities… I would have to advise against it…