Double checked bottom cowl edge and hinge alignment marks; marked high spots along bottom aft edge. Removed bottom cowl and sanded down high spots. Match drilled rivet holes for bottom hinges; clecoed hinges in place. Ground out access notches for hinge pin access from outside corners. Installed bottom cowl on fuselage and inserted bottom hinge pins; good fit. Positioned bottom cowl to precisely align side edges; secured in place, match drilled several rivet holes for side hinges and clecoed hinges to bottom cowl. Removed bottom cowl and match drilled remaining rivet holes for side hinges; clecoed in place. Reinstalled bottom cowl on fuselage with all hinge pins; good fit.