Installation of W-1011 L/R, W-1010R, W-1012L/R looks ok. The AN426 Rivets (2 for each rib) are positioned on the longeron flanges (one on the top and one on the bottom flange). They are not visible because of the tank skin.
The other rivet on the flange has been set when riveting the top/bottom skins. For the bottom outboard skins the rivets are NOT set.