I would suggest that the rear bracket be tension strength based only like a high tension bar with threads in both ends. As it is the shape of the flat bar at the rear anchorage works like a lever forcing the head of the bolt.
It would be nice to secure the bottom in some way that help the forward motion better. Perhaps a flat bar under the storage unit if this is bolted to the floor.
Ron it is correct in saying that it is nothing wrong in mounting on an thin aluminium panel providing that large plates are used to spread the load.
Cheers

