Recalled to work tomorrow, so decided to get in a couple of hours today. Riveted the counterbalance rib to the spar. Began riveting the couterbalance skin to the rib, careful not to rivet it to the spar yet. All rivets went well except one in the corner where the bucking bar slipped off the shop head. Successful drill out and replace. Installed the counterweight. Had to file small notches in the sides at the forward end to clear the shop heads of the rivets holding the skin on. Primed the weight and installed the screws, torqued to 23 inch pounds (spec was 20 - 25 inch pounds).