I decided to use the same technique used on the wing tip fairings, that is to add an aluminum strip on the inside of the fairing, rivets to the fairing, then match drill holes for the rivets.
Performed the usual deburr operations on the aluminum strip for the all holes. Counter suck the holes in the fairing for riveting the aluminum strip, the rivets the strips into place. I was then able to install the fairing on the rudder top, and pull into place for a flush fit, then rivet.
Aluminum strip riveted to inside of Rudder Top Fairing
