I've got a 1971 2800CS - I'm trying to remove the headrests to replace the little chrome plastic discs which sit at the base of the headrest posts. Breaking the old ones off was easy. But getting the headrests off - or even to move at all - is turing out to be impossible. I've got many manuals that say they're adjustable but none specify how. On my 1974 Bavaria, there's a hidden "secret switch" under the fabric of the seats that you push then you can adjust the headrests. So far, I'm unable to locate the "secret switch" on these seats. Any suggestions?