GMC Yukon Owner's Manual page 78

Q: What is wrong with this?
A: The lap belt is too loose. It will not give nearly as
much protection this way.
2-40
WARNING:
You can be seriously hurt if your lap belt is too
loose. In a crash, you could slide under the lap
belt and apply force on your abdomen. This could
cause serious or even fatal injuries. The lap belt
should be worn low and snug on the hips, just
touching the thighs.