Rivet platenuts on side angles for mounting the battery box to the firewall (3 platenuts). I counter sunk the pre-drilled holes on the firewall side of the side angle. Enlarged the center hole to #12 for the AN3-4A bolt. Deburr all the holes before riveting. (installed two platenuts on the left side and one on the right side as per DWG 31A).
