I followed the VAN's instructions and drilled a centre hole in each of the brackets for a 1/8 inch hole on one side and then drilled 6 of the 7 brackets with a #12 hole on the opposite flange for the nut plates. The brackets where then clecoed into place and back drilled through the spar. All went well and the rear tank plate seems to line up well against the outboard rib and joint plate. I just need to back drill the inner most L angle, not sure why this is done differently to the rest.
Close up view of L angle support brackets back drilled to the spar
