Lower Rudder Fairing Fitting/Hole Layout

I needed to true up the 2 long edges where the lower rudder fairing meets the skins so there's no gaps. I went to HD and bought a single 28"x4" floor tile for $1.89. It's very flat and dense. From there I taped sandpaper to it and sanded the fairing against it along its entire length at the same time. This evened out and trued up the edges removing high and low spots along its length. It now fits against the rudder skins well with no gaps. Then I started laying out the 18 screw holes for the underlying nutplates that will secure the fairing. It needs to be removable because the strobe light will be mounted in it. The other fairing are permanently attached with rivets.