Consider the load bearing ability of the floor where you put it. A buddy put one in a spare room/den/gun room. It was one approx. the dimensions you mentioned. He place it next to awall that had a bathroom on the other side of the wall. The tub/shower was on the other side of the wall. The grout around the tub was old and leaking, then the shower started leaking. The floor boards rotted. His kids mostly used this bathroom so it kind of went unnoticed. He came home one afternoon and found the bathtub, his gun safe and most of the flooring down in his basement. Took him a long time to share our laughter.
Well, I suppose I shouldn't laugh either..;-) You make a very good point. In my case, the safe will be on the ground floor on a slab. Thanks!