Its not necessarily the thickness of the material that makes it spinner proof, its the way you mount it.
For comparison my robot uses 15mm HDPE and consists of something like 150 screws. It has survived several spinner fights and hopefully will last a few more . Explosion, for example, only uses 4mm HDPE (I think) but is mounted on a hardox welded frame. I would probably say that 30mm is a tad excessive though, not sure though.

Hope this helps