I duct taped fairing to wing as close as possible to a flush fit for starters. Then I used a small washer and a black marker and rolled the washer along the fuselage, effectively transferring the profile of the fuselage skin to the fairing. That worked for most of the distance. The spacing gap in the remainder was greater than the washer could span without falling down under the fairing. So I redid it with a larger washer, hence two lines. I used tin snips to trim away the closest line (or equidistant from the 2nd line for a short distance). After using the scotchbrite wheel on the grinder to finish and smooth the edge, I used a 3/16 drill bit to gap the fairing and re-taped it. The rubber seal fit nicely in that 3/16 gap. Next up is drilling some holes.
Left fairing after transferring fuselage profile to it.
