I would get the tow ring out and install in the front for tiedown matching the rear, I feel the front is more important than the rear.

 

Yes, I agree (I haul canoe or a kayak). If at speed, the bow of the boat moves off center, it'll torque the crap out it and damage something: boat, car, other cars, pedestrians, farm animals, etc.

Back rope keeps it on roof when stopping but I'd use two ropes / straps down from the bow to each corner of the front bumper.

BTW, that seating position on the boat looks scary.