On the RH side of truck, I prepared a steel structure to hold the fridge and the safe. All of this will be hidden later by finishing panels.
The safe is to put my laptop, camera, passeport and $$$ in security. The steel structure is firmly glued/anchored to the floor and wall of cabin to make it very hard to be removed.
NB - The safe should be quite effective against casual thefts. Obviously "brute" force will enable a determined thief to get away with the safe...