Any tank that has a cross brace incorporated into the top rim is a bad candidate for de-rimming. If the tank doesn't have that cross brace the plastic rim isn't adding much more strength to the top, so there should be little, if any, problem with removing the plastic rim. But, when a tank fails, the amount of water that is dumped on the floor, through the floor to the room below, and into the electric wiring under the floor, and soaking into the hardwood floor, etc. depends on the tank size. If you would be bankrupted or would think about suicide if your whole tank of water was dumped on the floor, never, ever even dream of removing the rim!