Yeah, just plug the hole permanently. Unless you like running your a/c in 'fresh air' mode while driving Metro Manila.

Evem most small A/C shops can plug it for you without major surgery on the car.

Also had a similar scenario on my former Pajero. But what Norman (Mang Mario's son) did was remove the old foam from the flap. Cut up new foam (Uratex foam used for mattresses) and put new foam on the flap. I don't know how much it would've cost because sinabay ko lang sa cleaning (Php1,200).