Etdeb sorry to hear about the accident. Hope you and your family were able to walk away unhurt. I believe what you said about the trucks, just did not know that was a problem. What can an RV driver/owner do to avoid that? Slowing down to 35 on a 55 speed limit road is bound to piss off other drivers.
As to the original topic; I would not want my preps to be on display. Would it be safe, legal and possible to put in a false floor? In an RV I'd be leary of storing preps in a drop ceiling or in the walls for fear of throwing off the center of gravity. Another option would be to rent a storage unit in an home base area.
In most RV's, the "designated" storage compartments are either at, or below floor level. In most travel trailers, there is floor level storage in the front of the rig, usually accessible from one to two outside compartment doors, and/or underneath the bed platform (in front bedroom rigs). The remaining interior "mid section" storage is underneath the sofa/sofa bed, dining table benches, and kitchen cabinets/drawers - this storage is fairly limited, probably thirty to forty cubic feet on most rigs. The rear section storage in a travel trailer depends on whether it is a bunk-house model or not, there are typically exterior accessible compartments on most floor plans that open to interior floor-level storage that resides under the bunks, or in some cases rear master/queen bed platform.
In fifth wheels, most of the storage is exterior accessible and underneath the walking/living floor on the large section of the trailer. Most of these rigs have a large exterior accessible compartment underneath the raised section at the front of the rig, and exterior storage compartments lining the "edges" of the rig. The number and size of these compartments varies significantly by rig floor plan and manufacturer. A fifth wheel is easier to overload than a travel trailer, and generally starts heavier as well, so if you plan to tow one, you need to pay careful attention to gross weight. The real issue is first and foremost the tow vehicle's braking capacity, followed by rear axle capacity.
Many fifth wheels need a full one-ton, dual rear wheel two vehicle to be safely towed, as they can range in gross weight from 12,000 lbs. to 25,000 lbs. when loaded.
If you pay attention to how the rig is loaded for towing, most of the stored material weight will be low in the rig, and fairly evenly distributed over the floor frame and axles. Heavy, dense items like ammunition, canned goods, and heavy tools can create load "hot spots", so you have to spread these things out in the storage compartments.
Careful loading can also disguise or conceal prep items, while still allowing you to access them reasonably fast. I use various tote boxes (Rubbermaid) and pack certain things in these containers surrounded by bedding, paper goods, seasonal clothing, etc. to conceal the contents that are problematic.
Firearms are a more difficult problem because of varied state laws (if you are mobile), and the fact that a firearms safe is very heavy and difficult to conceal. The most straight-forward solution involves some custom fabrication and use of the space under the master sleeping platform to create secure storage for long arms, handguns, etc. Think aluminum and either carpet tiles, linoleum or similar veneer... if you can cut and weld with TIG, this can be a DIY job, otherwise it is something you have to have fabricated and possibly installed. I did this job myself.