Before I go on, I did discover one thing that I want to emphasize now before I forget. While bolting on the bottom wing center section for the first time I found out that I should've installed the blind nuts on the rear mount parts. The rear ones are "blind" so I had to go through major contortions to get the blind nuts in. I'll highlight this now:
!!!!!!!!!INSTALL BLIND NUTS FOR BOTTOM WING CENTER SECTION PRIOR TO ASSEMBLY!!!!!!!!!!!