Camper Shelf

I've been toying around with the idea of creating a shelf in my camper... inspired by Bajataco.com. I've come to the thought of mounting the shelf on the area right above the bottom of the camper (see images). This way, if I have any leaks, the water will leak under the shelf... bags, clothes, etc. can stay on top of the shelf. Surfboard, wetsuits, and fishing poles underneath. On top of that, I'll be able to secure the shelves onto the camper mounting bolts.

My original thought was to cut 3 plywood shelves (front, middle, rear) but since the sides of my camper angle in, it's impossible to insert the shelves (see images, again).

Now my next idea is to cut each of the 3 sections in half. Basically the same concept except the 3 sections now have a left & right piece (front left, front right, middle left, middle right, rear left, rear right). The issue here is I need some type of hinge / bracket to join the left & right. This way, I'll be able bend the shelf and then straighten it once the sides are in the camper's groove.

Is there some type of hinge or bracket that can withstand the board weight + more? I don't want to install a center support that moves to the bed because I still carry large items in my truck and I want to be able to easily remove the shelves when necessary. Any input is appreciated!