You didn't ask this, but you did mention expense.

I built my own rack for around $40 in materials. Capped galvanized pipe for the cross pieces, and oak for the rails. I used metal stock from the hardware store for the door frame clips and just spent some time with a bench vice and a hammer to get them in the right shape. It took about an hour to get the first one in just the right shape to grab the frame and still allow the door to close, and then 5 minutes each for the other three clips. Cut the oak boards to the curve of the roof and put some self adhesive foam weatherstripping on the bottom of each foot so they wouldn't scratch the roof of the car. A screw in from the top into the pipe keeps them from sliding sideways in the oak rails. Foam noodles wrapped around the cross pipes are all I need to cradle the kayak.

It's very strong. You can grab the ends of the boat and rock the whole car back and forth without the boat or the rack budging. It's not theft proof. Anyone with a wrench can remove it, but I don't leave anything valuable on it out of sight.