The snag with using a plain gasket is when the car is standing outside in heavy rain. Water drips between the body & lid, lands on the flat bit of steel that does the locking and ends up dribbling inside the cabin. You'll not even know it's happening and if you garage the car the likelyhood is you'll never have a problem. But if it's outside regularly then you build up cabin moisture and in winter the screen has a tough time demisting, plus you get assorted rust in places you never see !
If you have room to fit a short section of foam rubber on the body above the lock such that it diverts water around the locking plate, then I think that's as good as the little rubber sock, which usually tears over time anyway.
