Re: What safe are you using?
Zanotti Armor here - for the following reasons:
http://www.zanottiarmor.com/index.html
1. Can get any size I want into any room. Once it's all pinned together, it's as strong as any welded safe and heavy enough that it will take some serious effort to get it out of the house.
2. Can easily be moved, if/when I move. The biggest plus is getting it down the stairs into my basement. I don't have a walk out door down there.
3. Customizable interior - they'll build it the way you want it.
One thing to note - they do not contain fire rating material, but are fire resistive and good to 1200 degrees for 20 minutes. I keep mine in a good sized storage room in my basement which has sheet rocked walls, and very little fire load. No, I do not worry about having fire resistive board in the safe - as a 20 year veteran of a paid fire dept. I just don't feel it's necessary (in my application). Heat rises, so the lowest floor or basement will be cooler. Water damage is a much more likely problem, so I overbuilt at 2x4 platform covered in plywood for the safe to set up off the floor.
Back to the fire rating - if 1200 degrees for 20 minutes isn't enough, trust me, I'll have bigger issues to worry about, such as the whole house gone.
Fire board/gypsum/cement board protect by releasing the water they contain when they get heated to a certain temp., basically releasing steam on the inside of your safe. If the temp continues to rise, they very often break down further and migrate towards the lower sections of your safe. If the fire continues to burn unchecked, guess what, you now have little or no protection in the upper regions of your safe.
So, for me, no fire board/cement in my safe. If you really want to protect your stuff, soldier a fire sprinkler head or 2 in your safe room. If you also have a floor drain close by, even better.
I fully agree with the mechanical lock.