Always transport it right side up, the main forces are then on the hull which is more rounded than the deck thus stronger and more rigid. I'd want to spread the hull supports like the other guys are talking about too. A cockpit cover, which can be pretty inexpensive, keeps any water out of the cockpit.

Bow and stern lines to the car when long distance car topping and straps holding the boat to the rack, no ratchet straps either, too easy to apply too much force, just has to be snug not with huge force to hold it in place.

Bill H.