CYi5 said:
Adding some yakima crossbars wouldn't be a bad idea. They have brackets you can add for canoes.
http://yakima.com/Product.aspx?id=50
or Thule. Check them both out. When I use to be a kayak guide and seller we had both Yakima and Thule gear. Both are great and have there own advantages over the other.
Yakima uses a round bar, which is stronger, but using any attachments on them is a pain in the butt as saddles and cradles will spin on the bar and Thule uses a rectangular bar, which is a little less strong, but attachments you put on the bars will not move at all.
If you always have someone to help you unload the canoe then you will have no problem with Yakima. If you ever go out alone and have to load and unload the bars by yourself then Thule might be better.
I had Yakima first, but since I load my truck myself the Yakima bars became a hassle when I tried to get my boats into the saddle.
Both Yakima and Thule have canoe brackets that will keep your canoe in place.
These are the two biggest manufatures of racks. Yakima tends to be more west coast since they are a Washington company and Thule tends to be more east coast since they are now a Connecticut company.
Here is my Thule set up. Sorry no pics of my old Yakima set up.