One of the (many) good things about wood is that it is stiff. I think you would have some problems if you fiberglass-and-epoxy-laminated both sides of a bamboo mat. You would have two thin, strong sheets separated by a noodly material in between. I have a Royalex canoe (plastic) that has a farily flexy hull -- not just when scraping rocks, but also some buckling from just the pressure of the water below. I think the bamboo lamination would deflect similarily, puttng the 'glass/epoxy skin under too much tension, and would cause the epoxy would crack.

On the other hand, bamboo-like materials have been used to make canoes in more tropical regions. It would probably make for good framing material for a skin-on-frame kayak.

Dean