Today was hat stiffner day. I finished the flanges I did not get done yesterday. I installed the upper and lower stiffners after removing the inboard and outboard upper skins. Save the carton the skins came in. It is a good place to store them after you get your initial drilling done. I fabricated the block and steel plate per manual to adjust the ends of the stiffners. I used a long piece of scrap to simulate the skin to check the fit of the upper stiffners. I will double check square end flanges and next drill.