Next get some IPA and clean it even more. I used some cotton pads for application. This should remove all of the remaining dirt and grime. Do an additional wipe down with a clean microfiber to removing any small particles.
Once it is clean you can start the test fit on the shark fin. Make sure that your placement allows for clearance with the OEM antenna underneath the shark fin. I found it best to point the OEM antenna forward for the most space.
Take your time and carefully align the shark fin so it is straight. Step back from the car and make sure. Then add some masking tape to help with relocating it. I used strips all along the entire edge because I felt this worked better than just using 3 pieces like VG suggests.
Next get a flat head screwdriver and the appropriate bolt and washer. For Subaru you will use the smaller M5 bolt.
Screw the ring terminal onto the OEM antenna. Make sure to attach them in the following order, OEM antenna base, washer, ringer terminal, bolt. Due to the size of the items you need to have the washer between the ring terminal and the OEM antenna or else you will not get good contact (necessary for good reception). Do no overtighten.
I pointed the OEM antenna forward, the ring terminal up, and then bent the lead to it sits flat. This seemed to allow for the best fit. Now it's finally time to install the shark fin for good. Do one last check that everything is clean and dirt free. Then get your hair drier and heat the roof of the car until it is at least room temp (or slightly above).
Carefully remove the backing from the adhesive and apply the shark fin to the car. Be very careful to align properly using the masking tape as a guide. Start by pressing the front portion down for 1 minute. Then press the rear/entire thing down for 1 minute. Once it's stuck on you can pull the masking tape off and you're done!
Here are some photos of it installed:
So far I like it a lot! It looks much sleeker than the OEM antenna. I live in an area with good radio reception, and this does not seem to have changed. It is still just as good (or bad) as it was before. I will try to get updated pictures in daylight as soon as I can!