I needed roof racks to carry large items (such as drywall) from Home Depot. Searched onloine and all the available racks were more expensive than I wanted to spend. I took a good look at the racks I had from a previous car and came up with a modification to use on my Matrix (should work on a Vibe without racks too).
I drilled hole for bolts in the feet of the rack, and bolt them onto the roof using the locations for the factory rack, they are on solidly and secure (probably moreso than if they were attached by the clamps as they were on the other car), and no chance of scrapes etc from the mounting hardware. I don't know that I would leave them on for a longtime as I am not positive that water would not get in, but it only takes a couple of minutes to Re/Re them so not a big deal, and they do what I need them too. I still need to get it so I can use both bolts on each foot, and clean up some spots to ensure full contact of the head of the bolts with the feet, but other than that they are working well. Pics attached