GMC 2003 Safari Owner's Manual page 44

Never do this.
Here a child is sitting in a seat that has a
lap-shoulder belt, but the shoulder part is
behind the child. If the child wears the belt in
this way, in a crash the child might slide under
the belt. The belt's force would then be applied
right on the child's abdomen. That could cause
serious or fatal injuries.
Wherever the child sits, the lap portion of the belt
should be worn low and snug on the hips, just touching
the child's thighs. This applies belt force to the child's
pelvic bones in a crash.
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