Good advice…
I always thought that those handles were poor places to attach a strap.
Thule J Racks will be fine…
as will Yakima or any other reputable brand. I have Thule folding J-racks, so that’s what I know. I’ve used them on top of my saab 95 wagon, a subaru forester, and have never had trouble. Use good compression straps to secure the boat to the cradle, and don’t just wrap them around the boat and j cradle. Loop the compression straps under the crossbar as well. This will give you added security for the cradles. It is not unusual for a little re-tightening of mounting bolts in strong winds. At each gas stop, I check the mounting bolts to make sure they haven’t loosened up at all, and recheck the compression straps. After a while, they stay snug. Use front and read tie-downs for long trips. Thule j cradles come with all the compression and front/rear tied down straps. If your boat has hatches, bungee them and if possible, add a cockpit cover to reduce drag from wind getting inside the cockpit. If it’s a rec boat, this might not be feasible, but if it is, once again bungee the cover securely. I don’t get people who say “don’t do it”, there are all manner of vehicles on the road with bikes, boats, and other items on the roof. With proper equipment and common sense, and a thought toward safety, J cradles are a good choice. Maybe not the best, but if you’ve got other gear up top, that will help cut down the crosswinds catching the boat anyway.