Thanks for your feedback and I think you might be right . Seems the covers may somehow grab onto the interior metal override without any bolts. I was afraid to mess with them to much in fear of snapping them ? I may let them sit in the sun and warm up before I try again to pop them off .
more details from my memory...yes, must be a snap only. I remember that the nos I had last year, had already cut slots on the rubber just on the back to snap on the metal . So, if you catch the top rubber part from behind with one hand, lift a little (strongly) you will be ok. Maybe will need the bottom first, but I guess it will be shown as you do the first trials