Roof rack for hauling kayaks?

My wife and I would like to be able to haul two kayaks on top of our 07 Prius. I've done some research on here and seen a few different trailer systems that are pretty cool but haven't found anyone that has shared their experience with a roof rack system. I'm assuming that hauling boats on top can be done with a good rack system. Obviously it would drop the MPG way down and be a little squirrely on the road but as long as it's safe and we can bring our boats with us it would be worth the sacrifices to us.

So, is there anybody hauling kayaks on top of your Prius? I might add that our boats are 13 foot long, not little creek/whitewater boats. What kind of rack system is it and where did you buy it? How does your Prius handle while driving down the road? MPG?

Thanks for all your time and help!

 

I have seen other Prius owners hauling a kayak(s) on top but they are always going the opposite direction.

Anyone?