I use a set of saddles by Thule to do the job. My current ride is a little bigger, but I used to put two boats on my Acura Integra hatchback with no worries. These saddles make for easier loading and unloading, too.

If you don't like Thule, Malone of Maine makes a similar setup that a few of my buddies likes. Or if you're ready for a little project, you can make your own. Ross Leidy's site details the construction of a similar set of saddles in wood, glass, and epoxy. Custom fit!