I have no way to access the aft section, but do have two doors to the forward section in my Fox. I've been trying to think of a way to utilize these spaces...and I'd very much like to find a way to carry fishing poles.
Also, while not secure,,,,these spaces are out of sight, and very hard to get to. A larger box would be nearly impossible to get out over the bed rails. I can't even get my arm in there with the camper on.
A waterproof/resistant duffel is a good idea.
I'd love to see pictures of others setups for storage in these spaces.