Here is version 2 of the idea above. If you have soft tie motorcycle style tie downs, the straps slip between the crossbars and the headliner a lot easier than the hooks.
Ratcheting cargo bars. I bought 4 from Home Depot and then cut them down to fit. They store easily behind driver's seat. I break them out on very windy days or when I don't feel like unloading the roof rack. One in each corner.