I purchased a 1" diameter neodymium magnet N52 strength 1/4" thick on eBay. Stuck a 1/4" diameter foot long rod to one side then snapped the magnet down on loose chair screws under leather. Twisted the magnet with the rod. Large N52 grade neodymium magnets have insane strength.
I would purchase a packet of smaller less powerful discs then slap one atop each affected screw. These magnets will not turn against the roof coating and they dang sure will not fall off. Beats wrecking a roof coating.
Your mileage may vary :)
