This is the best photo I can find of tying down in that era. It's still pretty representative of the method I use today. The web straps supplied with the kayak carrying devices are used to strap the kayak to each device. The orange web strap (a friction tightener - definitely not a ratchet-type tightener) on each kayak at the bow and at the stern. At one time I even attached a spring line from the car's forward cross bar back to the stern to inhibit the rear rotating, but that didn't stop it. I now use the rope-type ratchet hold-downs supplied with the carriers instead of the orange web straps, but am careful to just snug them up, but not nearly enough to oilcan a poly boat.

With the Yakima racks nothing could stop the rearward rotation. With the Thule racks I have not seen the issue again. (I have no financial or other connection with either company.)