Bamboo, or any backing that is considered a "hard" backing will need a perfectly flat surface to glue to. If you are just looking to add couple pounds, maybe you could just shorten an inch or so off each tip, and re-tiller.
So I got a maple board bow bending last night. It's 52# @ 21" right now. I'll post a pic or two when things progress a little further.
Tattoo Dave