I use one of these to carry my 14 foot canoe on the roof of my ZX2:

http://cgi.ebay.com/ebaymotors/ROOF-...mZ260254467380

The roof of your Cobalt is stronger than you think, especially around the door jambs/headers. That is where the main structural support for the roof is located. These really work well. I tie the canoe down bow and stern, Ford/Mazda leaves the tie down hooks on the frame of their vehicles. I can travel at 70 M.P.H. in cross winds and that canoe is steady as a rock.