fisherman, sorry it took so long to getback to this thread but I finally remembered to take a look at my own Expy for reference. If you flip up the 3rd row headrests, sit in the seats facing the rear. Push the fabric down down about 1-1 1/2" you will see there is a clip (2 per headrest). It's tough to get to but it's there.
You can only access these from the front looking back.
Good luck
Matt