Marked all "no-rivet" areas for flap, aileron stop and pitot tube. Began riveting. Aft channel first, then rear ribs 1 thru 9. Began front channel. Some challenge to get rivet inserted fully through front hole of rear ribs. Tendency for the rib flange to bend. Rib 1 - 4 are easy to verify by touch. Rib 5 wil be a the toughest one. May wait until wing is flipped over and top skin is removed.
