End to end. ie end grain joints are very weak on their own. Yes, the back and belly full length lams theoretically should stop it from coming apart. I've never seen anyone try it. To me you are introducing a lot of potential weakness into a structure that relies on strength to function properly.
It would be easier to use a strip of laminated(side by side strips) bamboo(available commercially, the type fglass bowyers use as cores). Other options: use a wood lamination; use a flattened strip of bamboo, or even scarf joint of several pieces would be stronger than the original idea.
