Here is another way of attaching your GoPro to your kayak. This uses the GoPro Handlebar Mount and is shown attached to the Eskimo Topo Duo I own. The handlebar mount will only work on a kayak if the grab handles are solid and thick enough.
This will work equally well with the Hero 2 and 3. In the image you can see I have used a leash just incase the camera gets knocked free and a Floaty Backdoor has also been added.
More GoPro stuff here – Click.