If you are in a situation where you need to stack kayaks—such as when transporting them on your roof with no rack—it’s okay to stack the kayaks with the cockpits facing each other. Use a strap to secure them in place. However, if you have to do this, you’re better off placing them side by side (again with the cockpits facing each other). This prevents either kayak from bearing all the weight of the other, and the sides are sturdy enough to avoid warping or deforming while they’re strapped down.