Iv'e got about (50) 2" squeeze clamps that I distribute throughout the length of the bow, so I figured that I had decent enough clamping pressure. I don't have access to a metal plate, so I think what I'll try next is wrapping the whole thing in electrical tape. It's rubber, it stretches, it doesn't slip, it's cheap and disposable, and it holds with an awesome amount of force when stretched out...
I tried the rubber band method before, but unfortunately I had a really bad Mel Brooks moment with it. As I was wrapping the bow up, a piece of it actually snapped and when it sprung back, it laid out a nice red mark across my cheek. I swear, it was worse than the time that I gave the WRONG answer to the question "does this make me look fat?"