Had time for a second session later in the day so I updrilled the rear top skin to its final rivets sizes. I also drilled out and updrilled the rivet line connecting the rear top skin to the rear and forward upper longerons.
Rear top skin drilled out to A4 rivet size, except at the longeron splice where it's A5 rivet size.
Completely updrilled rear top skin from the tail area.