I like the idea of the aluminum, but I would also sand/grind around the the cracks to remove the loose stuff and the seal it with some epoxy to prevent water water from getting into the wood framing around the edge.
The boat building epoxies like West and System 3 are easy to use and available in small quantities.
My 30C1002 which is a totally different animal construction wise sits on a square steel tubing frame in the bed that I made as the the overhang is too long and the floor started sagging. I filled in the gaps between the framing with rigid foam insulation.