It looks like your tank has what is called a "floating base" (a rim around the bottom edge which raises the bottom glass above the surface the tank will be on.) If that is the case then it is not advisable to use any sort of crushable mat because the pressure under rim will be enormous and will smash any compressible material I believe. You also don't want a mat to add "flexible" height, because the enormous weight, being able to "sway" even a tiny bit is an increased instability.
The idea of needing a mat usually comes from its need under pure glass tanks which have no floating base rim. Those tanks do indeed need a styro mat of some sort ideally to even out any spot pressures on the bottom glass.
There wouldn't be anything wrong with using some plastic sheet (thick plastic bag type material) if you want to protect your stand from possible small water drips. Also, leveling is worth paying attention to, as perhaps the stand itself will need some help being level. If you use shims, large surface areas are better than small.
~~waterdrop~~
