1. Today I riveted another fuel tank support to the top skin and about 3 rows of rivets. 2. I took a prop level and checked the slope of the skin at the rear spar. i set it level at inboard edge and then checked the slpoe at the outboard edge of the rear spar. They are the same so no twist. I also checked in the middle of the rear spar and it is the same as both ends. 3. I then drilled all of the holes in the rear spar top edge and top skin. Then I deburred all of these holes on all 4 sides: two skin, two spar..