Before riveting on the bottom skin I’ve decided to prep and drill the wing tank cover and inspection covers for nut plates. Since access to the tank cover aft row of nut plates is aft of the rear spar it make sense to sequence in the riveting schedule to include the nut plates. It would be harder to get to after the aft skin is riveted on. I drilled all the nut plate holes using the nut plate as a guide.