One option is the Nascar nets or Train nets ... Basically they are the big webbing that you can attach to the bottom of the bunk and then attach to the roof. Run a good solid piece of wood across the ceiling that the net will mount to. Plus, you can also put some nice wood up the ends to help support the top brace.
Do a little crafts with the stain and it will match the wood on the bunks.
2013 Georgetown 351
Much more significant other....
2 Kids and a dog that rules!