Stand sag- dangerous?

I am an engineer, as such I like data. Unless you had identical tanks, the same size stones and dropped them onto the tanks from the same heights and at the same angle, measured the results and repeated this process numerous times to record and compare the outcome, your above mentioned example is meaningless. And accidental dropping is just that, accidental and random, anything can happen.

I am not going to argue with you, I do put all my tanks (around 40, big and small) on polystyrene sheets which are lying on top of a flat wooden board/base. In some instances I use stand, poly, wood board, poly and then the tank.
You are however entitled to do as you please, just make sure you haven't even got the smallest of pebble or substrate grain on your board, otherwise you'll have a cracked base in no time.

 

On this topic, ...recently I read an article by the technical director of one of the bigger tank building companies in the States, and he stated (amongst a lot of technical explanations) that they recommend to put their tanks on poly on stand without boards.
Just like what pHish_man did with his 2m tank.
I had a 1.6m tank running like that for about 5 years before leaving the hobby for a while due to work commitments, ...no problem whatsoever, tank was 1.60m x50 cm x60cm high (10 glass).
Having said that, today I add a board.

 

@JCL well where is the data proving that polysterene under a tank is safer then a solid board? If you have pebbles where you put down your tank I have little hope for that persons tank anyway. I did not say poly does not work only that I think a solid base is better. So with due respect..

 

Ok guys both of you have made your points. Some will use boards and some won't. Let's leave it there and get back to answering his question about the sagging stand.

 

Question's answered thanks. The debate made me realize that styrofoam is actually a necessary compromise, but a compromise nevertheless.