I trimmed the bottom rudder fairing this evening. I worked the square hole where the metal tee was bit by bit to keep from cutting the hole too large. Next, I cut a hole for the rear position light/ strobe. I was able to find a washer almost exactly the size I needed for the hole... so I used it to mark the hole. Everything fits perfectly.
I still have to figure out how to keep the position light/strobe in the fairing. It doesn't seem like the small screws will do the job sufficiently.
