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 area above the rear wheel, received some rigid insulation board at the walls first, and then filled up with house insulation,
The final result.