The wife and I both wanted STi wings on our WRX limiteds but wanted the fuel efficiency of the 2.0's. We decided to go ahead and get wings direct from Subaru and have them painted. When they arrived I took them down to my local paint guy and he gave me a deal on painting hers red, and mine WR blue.
The boxing that Subaru sent these things in was far beyond what I would have figured. Boxed, wrapped with bubble tape, and foam coverings for the bases kept everything quite secured. I was actually very impressed, as was my paint guy. He pointed to a new part from Ford (rear bumper) that came in thin clear plastic via ups and told me that this was the norm for him.
I started by washing the deck and removing everything from the trunk, except for the little cargo tray that Subaru put in the car, what a godsend that was. Remove the liner panel on the inside of the trunk deck. I used frog tape and ran the first piece from the front of the trunk deck to the rear, leaving about 3/4 of an inch over the seam. I rolled the extra over the seam to keep any of the tape measure edges from damaging the clear coat. I ran an additional four strips with just a bit of overlap on each piece. I gave the passenger side the same treatment. I also ran two strips in the middle of the trunk for alignment purposes.
I then took a measurement from the rear part of the trunk at the front edge of the existing lip spoiler to the other side, pulling from driver side to passenger side, keeping the tape straight. I marked center of the trunk at the back edge of the trunk. I then pulled 5" down from the front edge of the trunk deck towards the back, on each edge of the trunk, making witness marks on each side. Then you can pull a tape ( I used a cloth tape for ease and safety of my clear coat ) from mark to mark, get your measurement, and mark the middle of the trunk near the front edge of the trunk deck. Draw a line from the front of the deck to the rear using these marks and you now have a center line for your trunk deck.
I set up a pair of saw horses with a piece of 4' X 8' plywood, and placed towels on it covering all of the wood. The STi wing will come with 3 ten mm bolts installed in it already, as well as 3 plastic centralizer pins. 2 of these pins can be slid right out. The last plastic pin felt like it was popped in, and me pulling on it with a pair of pliers got me the pin part leaving the head in there. I was not sure if it would be recessed far enough, so I took my handy 6" grinder with a cut off wheel and proceeded to gently trim the base away. before long the pin was recessed into the base of the wing. You have one on each side to do.
The box that the wing came in was perfect for a template, I just removed one of the flaps that were long and set it under the wing. Push the metal studs through the cardboard on each side and trace the bases on it as well. Once you have that done, you can trim the cardboard so that it is easy to work with. One thing of note, between the 2 bases you will want to make the cardboard a little more narrow than both the top and the bottom of the bases so that your template does not hit the glass of the rear window when you lay it on the trunk deck. Now you can pull measurements between the opposing holes of each base and make a few center marks on your template.
Having center lines on your deck and your template you can now match them up and figure out where you want to make final placement on your deck. I gave myself about half an inch between the base of the wing and the existing lip spoiler, and it matched everything up perfect. You will want to mark your stud holes with a pencil on the frog tape and double check everything by tapping on one side of the trunk while having a finger in the other side. If everything fells good and looks good ........ drill holes with a small pilot bit.
After drilling pilot holes, double check alignment by lifting the trunk and looking from the inside. You will see two holes on your frame of the trunk that you will have no problem getting a 10mm deep well in, the last hole ... well it should be right in front of the box tube that is your hinges for the trunk deck. I used a #9 unibit to make that hole about 3/4" big. The front hole has only the trunk deck to go through, the one that is closest to it has 2 more layers of steel after you get through the deck. The hole that is off by itself is the trickiest one to do. You have the trunk deck, then part way down there is a piece of reinforcement steel, then there is another sheet of steel to go through, but you can not put too much pressure on the drill bit or the bit will walk away and your holes will not be straight. This is the hole that you must also drill from the other side to be able to put your 10mm nut on.
You may have to manipulate some of the interior sheet metal to get the nuts to sit flat and proper. One of the things that I had to use on 2 of the holes was a burr grinder bit. You can get one at a Napa or and Autozone, maybe even Lowes, but you will want one of these for sure before you begin. Test fit the wing and make sure you can get all of the nuts started and once you are able to run them all down, apply a small bead of clear silicone around all six studs and put the wing on, tighten all 6 nuts and enjoy your STi wing.