I followed the shop instructions for drilling the Z brackets. They were centered and clamped under the main spar and drilled using the holes already present in the spar. The #12 drill is a precise fit for the holes in the spar and the AN bolts used to attach the brackets to the spar. Therefore, it is necessary to get the platenuts exactly centered related to the spar attchment holes.
Normally, I would cleco the platenut to the aluminum stock and drill the rivet attachment holes. This time, however, I inserted the bolts to guarantee the platenuts would be exactly centered, drilled, countersunk and riveted the nutplates in place. They should be a perfect fit. By the way, I used a deburring tool from Cleaveland and an electric screwdriver to do the countersinking. This method is quick and easy for small tasks.
