I enlarged each of the 4 holes in each of the metal ceiling ribs and installed a riv-nut in each hole. I ripped some 2 x 4 material and scored it so it would bend easily and conform to the bowed shape of the metal rib on the roof. I filed a piece of threaded rod to a sharp point, screwed it into each of the riv-nuts, and used it to make a template so I can duplicate the hole pattern from the metal roof on the wooden ribs and the plywood roof panels to be installed.