Another possible mounting method would be using strong cord stretched between a single screw on the top where there is likely some frame structure and a bottom screw to keep the line taut.
My concept would be to use wire shelves and "S" hooks mounted at the appropriate levels. The shelves shouldn't jump out of the hooks while underway, but if that is a concern then the hooks can be crimped closed.
The hooks would be tied into place. I would use a bowline knot at the top. Two half hitches with a lock, or figure "8" loops would secure each hook. The lines can be pre-fabricated using a long enough board using a top screw anchor. The hook locations can be marked on the board to assure consistency. The lines would then be installed and tensioned to the bottom screw as the last step using two half hitches and a lock.
Strong nylon or Dacron cord would work. High tech line would almost guarantee no stretch over time.
APS: High Tech Single Braid Sailing Lines
I would simply use a wood screw or deck screw at the top and bottom.
You will be installing the screws in a strong, relatively safe area for penetration.
The shelf heights can be adjusted if your needs change.
It is a strong, inexpensive, and relatively easy install.
The shelves may shift a bit and may scuff the interior. A single stabilizing screw cable tied to each wire shelf should solve that issue.