Fabricated jig for countersinking #30 rivet holes in Skybolt flanges. Set up micro stop countersink for #30 holes. Countersunk all #30 rivet holes in remaining stack of flanges; removed flanges from firewall, countersunk #30 holes and clecoed back into place. Began smoothing inside areas of top cowl nose to fit joggles on bottom cowl. Clamped cowls together at nose and drilled temporary cleco holes to hold the front halves together during fitting of bottom cowl.