Skidoor

Hi, I have the factory roof rails and I'm looking for a crossbar setup for a canoe or kayak which is designed specifically to attach to the OEM rails. I believe they securely lock into the grooves in the OEM rails, all I can find are crossbar mounts that seem to clamp onto the rails and seem to be a multi-fit design for different vehicles. Any advice? Links to specific "models" would be good.

Also, for those who have a J-style kayak rack system, what is the advantage to having the kayak mounted vertically like that as opposed to laying flat? Thanks in advance.