With the forming blocks ready to go I started to form the rear ribs. After clamping them between the forming blocks and putting the assembly into my workmate, its fairly easy to hammer over the flange. Working slowly so as not to stretch the aluminum too much I can almost get the flange completely formed before pushing material into the fluting notches. For the flutes I use a 1/2" drive socket extension and the same forming hammer. The flutes look very nice and the ribs come out almost flat.