The rear storage on the 233S is a very small space from the factory. I removed the right side wall (4 screws) and finished out the walls with 1/8" panel board to extend it another 3 feet. Reinstalled the side wall at the end of the extended space. It is a very tight space to work in but doable. Now I have a place to keep sewer hose, water hose, leveling blocks, tools, etc... The 233S does lack storage from the outside so every little bit helps!
2015 ROO 233S
2013 F150 Eco Boost