Hidden would be a safe's best asset in an RV as that is the premise for most wall safes, it is not that they are so secure, just put in an ideal location that thieves wouldn't look for...
As an example, in an RV such as mine, it has an access panel for the bath tub faucets and plumbing, a small piece of paneling on the hall side that merely slides up or down, so a floor safe under there under the pipes would be a good location, if you follow the reasoning... Cover it with a box of mouse poison and no one that opened the panel would give it any thought...
Pull out your drawers in the kitchen base cabinets and put a floor safe there as not many would pull out drawers to look for what is beneath them...
Hidden in plain site is another trick...