[Porsche-O-Phile]

Make sure your slab is rated to handle the weight. They can get VERY heavy. Even the somewhat small commercial-grade safes used on some of my projects for fast-food establishments require a 6" pad (on top of the regular slab-on-grade) to prevent cracking and damage. It sounds like yours would be larger.

Obviously these need to go on the ground floor - or in a basement - unless you're going to strengthen the bejezus out of the floor (I'd have that designed/calced out).

Depending on your situation and how long you're planning on being there, it might be easier to construct a vault. If you want to go this way, PM me - I've got some information on bank vault construction, details & information you might find useful. The nice thing about a vault is you can make it any size you want. The bad news is they are not cheap (lots of reinforcing - more than you'd probably think).