Whats wrong with my rig? https://mega.nz/#!C3hinCwa!h_3F6_WkF8-Cm4iLqbBorElmumhXKJnDnelBMFN3X_0

There's the blend file. I need it to bend backward in sort of a 'U' shape, but it bends and contorts in odd ways. I need to get this done asap as a client needed something done in 2 days, so I'm having to learn blender rigging on the spot. Anyone who can tell me what I need to do would be a hero. I tried turning on preserve volume which keeps the mesh from changing sizes, but it doesnt bend back as much as I need it to.
Ok, so, radical solution, follow these steps: