I know it would be a hassle to remove the safe but if you can bolt or screw some pieces of 2X4 or 2X6 inside the wall opening it would be easier to mount it securely and at least a little harder for someone else to rip it out. Definitely get some closed cell foam (like a sleeping bag pad) and line the inside. Don't leave anything in the safe that will absorb moisture from the air(that includes the holster) or you will have problems with corrosion. Try to come up with something to camouflage the safe so a thief taking a quick look in there will move on. A piece of white poster board taped to the wall will make it almost invisible without good lighting. Good luck to and your family. I hope you never need to use it.