Ah, billt, movin' on up, eh? ? ? ? ?

I had a very nice doublewide once, did not have a gun safe in it.
HOWEVER, I also did not have a basement, and I lived in tornado country. I was a mite spooked, especially after the granddaughter moved in during the summer of '07.
FWIW, I would find a site where the home can be put on a basement/foundation with a walk-out for the basement, and put the safes in the basement. Also, basement-mounted modulars are more secure and usually looked at differently by the local .govs. I actually had to buy a title ($5 and an hour of my time) so they could shred the title, just because mine was on piers and still had the VIN plate.
My new safe is in a corner of solid reinforced concrete walls and floor, so 50% of the access is secure (2 sides and bottom).
Also, check with the modular manufacturers on their recommendations for support. They can build something to spec too, if it is needed.
Also FWIW, I heard that modulars will start to shred at 120-130mph winds, whereas a true stick-built will start at around 160mph.