Yea that makes sense in a car, where you are traveling at 60 miles per hour and the weight of an adult can crush a child to death. I wonder about a tractor, however, when it is just your weight and not the velocity of the vehicle that is acting on the child (save perhaps a bit as it goes over). I know that my 165 pounds would NOT kill my 90 lb. daughter in this situation, though I'm sure it would result in some injury. If I have to depend on myself to hold on to her, what if I can't/don't? Yes, I am definitely talking about low and slow but there's always the possibility something could go wrong. I could just as easily (perhaps more easily) concentrate on holding the steering wheel to keep my body weight from crushing her. But the added insurance that she could NOT slip out would the difference. I know I'm getting into some fine points here, but what the heck...