Enlarge seat back rivet holes from #40 to #30. Match drill F-741A L&R tunnel cover support and F-741B tunnel cover to #30 from #40 using the tunnel cover skin (tunnel cover plate was drilled in previous step - 12/05/03). Countersink the tunnel cover skin for NAS 1097AD4-5 rivets (the skin is too thin for the AN426AD4-5 rivets).
