Installation of Inspection Panels in the baggage floor to inspect the entry step and to facilitate routing of electrical cables and antennas. Positioned reinforcement plate to determine position of the hole. Matchdrilled with #40 drill for flush rivts. Cut the hole and filed to measure. Countersunk nutplates rivet holes on the reinforcement plate. Countersunk all the holes for riveting to the floor panel. Tried to dimple but not very happy with the result. Much better with careful countersinking (backing plate to avoid drill wandering and oval holes). Backing plate was already primed therefore i riveted all nutplates.