Use Olympics dipped in Vulcum. You can also use a dipped screw if so inclined. Then, what I would do is clean up the roof panel area an paint it with white Sealoflex or Ceramaflex. That will increase the sealing of all seams and rivets as well as giving you some reflective insulation there in Louisiana.
"If it can't be reduced, reused, repaired, rebuilt, refurbished, refinished, resold, recycled or composted
then it should be restricted, redesigned or removed from production."