I drilled these holes and then clecod them to the spar. I was careful to make sure that they were true to the spar. Then I clamped one side and then drilled the holes for the other side. The I inserted another cleco and drilled the other side.
I drilled the nutplate rivet holes by first bolting on a nutplate with a short bolt and 5 washers. This made it so that I didn't have to thread through the squashed part of the nutplate. After doing the holes I deburred and then countersunk the holes on the drill press. Then I riveted on the nutplates and bolted the z brackets to the spar. The inside z bracket has nut plates on the spar. I'll get to these tomorrow.