The FLATED Air-Carrier sounds too good to be true – almost gimmicky. I mean, come on: a big, lightweight, rugged rooftop cargo box that installs easily in minutes? And then packs down into a duffel ...

“Held up through extreme heat and a storm.” ...

With everything from luggage and toys to pillows and blankets packed into the cabin, the annual family vacation or summer road trip can often feel cramped and stuffy. And the driver's sightlines?

To find out which options are actually worth buying, we gathered a selection of hard-shell cargo boxes and soft-sided roof bags, assembled them as needed, and mounted them on our Hyundai Santa Cruz.

“It’s easy to connect to the roof.” ...