The area under the bed is divided in compartments, from front to back: batteries, toilet, inverter & solar controller and bed linens with some extra space available on top of the wheel casing. The battery compartment allows a maximum of 4 batteries with a vent hole to the outside. I put the toilet next to it, to act as a separation between it and the electronics.
The front wall of the electronics compartment (here on center/left), is a piece of ½” ply, that will support a inverter, controller and possibly a converter. To make access a little bit easier, I made the right wall (¼” ply) removable.
The area above the rear wheel, received some rigid insulation board at the walls first, and then filled up with house insulation,
The final result.