I used to hit it all the time which never did anything.
I can take a picture later but I've had a folded up piece of card stock, that used to be a pack of Five gum, stuffed into the rear right corner. No squeaks since my 'fix.' Does it look good, fuck no. Does it bug the shit out of me anymore? Not a bit. I've been meaning to cut it flush but I need a sharp new razor blade and haven't bothered. I figured out where to put the card stock by pushing on each corner while driving until I figured out what stopped the noises.
I say stuff some black paper in there and cut it flush. Fixed for free