Graco NAUTILUS SNUGLOCK LX Instruction Manual page 79

A snug harness should not allow any
slack. It lies in a relatively straight line
without sagging. It does not press on the
child's flesh or push the child's body into
an unnatural position.
14. Raise the Chest Clip to Child's
Armpit Level
15. Check Tightness Again, Tighten
More if Needed
79