There is the slightest curvature on the fuselage skin along the top side of these NACA vents. I know proseal would hold it tight but I wanted some insurance. So, I drilled symmetrical 4 holes on top and bottom. When the vents get prosealed in place along with these rivets it will be absolutely solid. I put doubler riveting strips across the inside top and bottom rivet area to reinforce the NACA vents where they get riveted.
Drilled #41 for 8 holes
Excellent result especially on top 4 where skins has slightest curve
When this gets prosealed it will be solid tight!! Thats all the rivets required
