How about the Thule 630 Ranger 90 http://www.rackattack.com/product-pages/thule-630-ranger-90.asp? It has a reinforced base so it wouldn't dent the roof and it is weather proof as well. I'm debating about getting one for myself.
Reviewed here http://www.youtube.com/watch?v=YY_SWyjozCA.
Year: 2010
Location: Lawrence, KS
Trim: Sport
Tranny: Auto
Any extra accessories: none
Sale Tax Rate: % 8.85
Price you paid for your Mazda5(including tax, title, fees) $14,700
Bought last month with 34k miles.