Propane bottle on rubber or tile pad

Less than 2 years old and propane bottles and propane holder have rust on them. Waiting for rain to stop to re-paint. Going to cut up chuck of rubber or tile to put where bottles go in trailer.

Somewhere I remember reading an article that propane bottles need to be secured, metal to metal contact to ensure they are grounded? Really can't remember where or why and frankly I could be remembering wrong.

At any rate is there any problem cutting up a chuck of rubber or tile and putting between bottom of bottle and the holder?

Already measured one of those plastic tank holders you put on the bottom of tanks. To big for cover to close.

Thanks