Thanks for the info.Oh - BC - almost forgot - whatever safe you end up with, I STRONGLY suggest you use at LEAST one one piece of 3/4" plywood as underlay support for the safe, and go under the trailer and beef up the flooring from underneath. I've seen more than one safe warp the flooring on a trailer!!! Try to install it so that it "straddles" a crossmember if at all possible.
My Ft. Knox weighs in at 1800 lbs - no way I'd trust it in ANY trailer.