When Reattaching the Factory Spoiler...

I used rubber/cork gasket material and water proof sealant. Cut the size patches you want out of the roll of gasket material and use a hole punch for the stud holes (size of punch doesn't matter, the studs will go through the hole easily, tighter the better). Coat the underside of the patch with sealant and let it cure for 15 or 20 minutes before reinstalling the spoiler. Piece of cake AND 100% water proof.
 
Daggar said:
I used rubber/cork gasket material and water proof sealant. Cut the size patches you want out of the roll of gasket material and use a hole punch for the stud holes (size of punch doesn't matter, the studs will go through the hole easily, tighter the better). Coat the underside of the patch with sealant and let it cure for 15 or 20 minutes before reinstalling the spoiler. Piece of cake AND 100% water proof.

Sounds similar to what I was thinking except I was leaning toward all rubber. Reason is my 1992 Limited Edition 'vert had rubber and brass washers in this area from the factory.