In case you (or anyone else) wants to completely eliminate this leaking grease problem, the solution is to put sheet metal strips across the slots, attached just above the tops of the slots, extending downward almost to the bottom of the slots & inward (about 1/4" horizontal gap) at the bottom. This also greatly reduces the excess air infiltration these grils have during windy conditions. It takes three strips of sheet metal, one for each of the three sets of excessively large vent slots.