You want to be able to take it on and off whenever you like? If thats the case you could use the plugs mentioned above, but i wouldnt do it in the rain because im sure they would leak. I also think it would look kinda weird because you could see those things protruding out of the rear deck.
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Never argue with an idiot. They will only drag you down to there level and then beat you with experience.
all I did when I had mine off was use small peices of flat plastic and duct taped the underside of
it to cover up the holes (from underneath the deck),worked great,looked great!~
When I had my spoiler off, I had some touch up paint laying around so I actually painted the top of the plastic plugs. It blended in really well, from a distance you couldn't see the plugs. I also used some sort of clear silicone to seal 'em up from the water.
Now that I type that I see this thread is a few weeks old...but it is solid info nonetheless
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"Then there are sheepdogs," he went on, "And I'm a sheepdog. I live to protect the flock and confront the wolf."
Well, in the interest of commenting on week-old posts, I'll chip in.
You can do better than the "plastic-plug" route in a very similar fashion. I made metal plugs from 22 ga sheet metal, formed to fit the holes precisely. This was done by first cutting rough squares with tin snips, then slowly sanding down to the right shape. It's super easy, you just need to do a lot of light sanding/check-fit/sand/check-fit/sand some more/check fit for the 10th time, etc. These were mounted to a large back-plate that was sealed to the inside of the trunk. Paint to match, and amaze your friends.
I did this to fill my trunk lid holes, so I used 3M Small Metal Panle Adhesive. This is a permanent metal adhesive, so I then just treated it as a regular patch (filled the edges, sanded, and painted/blended). However, you could do the same with a non-perm sealant too (like silicone, etc.), and then simply push them through whenever you wanted to mount a spoiler back up. The bonus is that with the backplate's size, there's a great amount of area to put sealant on, so you won't have any leaking problems.
Here's a pic of the plug before it was painted. My car is Tungsten, so the damn bare metal was almost a match for the paint!
Remove rear Spoiler
