Please help with headrest removal

Please someone help!! I have a 2000 Grand Marquis and need to get the headrests off in order to put on seat covers. There is no button to push to release the headrests, just caps between the posts and top of seat. I unscrewed the caps to see what was holding the posts on. The posts are surrounded by what looks like black plastic "hands", 4 of them. I believe these help in adjusting the height of the headrests. No matter how hard I pull up the posts will not release. How on earth do I remove the headrests? Thanks for any help!!

Here is a link to a Crown Vic forum that someone is trying to remove the headrest.
http://www.crownvic.net/ubbthreads/ubbthreads.php?ubb=showflat&Number=2330201