We have a hidden place in our 5er and added a pistol Gun Vault (no pistol) more to hold things together. It will hold our passports, some private personal papers, a good wad of money and some jewelry and other valuables. It could have been a wee bit larger but our hiding place is big enough and probably secure enough for any overflow. As far as your lide out spot, there are places in every RV that just take some looking and maybe a mild mod, i.e. false end of an overhead cupboard, bottom of a base cabinet or even the rafters of the 5ers basement
The one we have:
https://www.amazon.com/GunVault-NV20..._89%3AGunVault. Cabela's has a nice one as well