Knocked out a few easy tasks this afternoon. Had the desire, but the garage was just too blasted cold with a 45 mph cold front outside.
Drilled 4 holes in rear seat support rail (2 ea side) to allow fuel lines, electrical, pitot-static, etc., transit from the aft fuselage to the forward. Once the seats are install, there's no penetration from rear to the front. The holes shown in fig 2 below will have grommets to prevent chafing.
Riveted a section of L-angle to the rear seat support SSO-2 to allow mounting to the armrest side panel.
Installed the forward-most side skin to the fuselage lower and upper longerons