GMC 2006 Yukon XL Owner's Manual page 69

Third Row Bench — Extended Models
For Regular models, do not secure a child restraint in
the right front passenger's position or the third row
driver's side seating position if a national or local law
requires that the top tether be attached, or if the
instructions that come with the child restraint say that
the top tether must be attached. There is no place
to attach the top tether in this position.
For Extended models, do not secure a child restraint
in the right front passenger's position or the third
row outboard seating positions if a national or local
law requires that the top tether be attached, or if
the instructions that come with the child restraint say
that the top tether must be attached. There is no
place to attach the top tether in this position.
Accident statistics show that children are safer if they
are restrained in the rear rather than the front seat.
See Where to Put the Restraint on page 1-57 for
additional information.
1-63