I got some help from soon-to-be Sling TSi builder Yeol Grant as well as ongoing support from Rosie (who did not want to be photographed for this riveting spree). On this part, I needed to be really careful of the Rivnuts. In addition to one in the corner of the skin that goes on the spar that needed to be opened up for the M4 bolt (screw?), there are two other M4 rivnuts that needed to be put into the bottom rib. That would have been good to see on the page that was showing the other rivnuts! At least I saw it before riveting the skin on. I also opened up the skin so the head of the rivnut didn't keep it from laying flat.