Right hand fasteners of Rotax Fuse Box is coincidentaly allmost a perfect fit to the existing fasteners on the firewall. I made-up a drill bar with a matching hole pattern to the 3/16 inch Fuse Box holes and clecoed the bar to the fire wall such that the 3/16 dia holes are within the smaller 1/8 dia holes on the firewall. Then drilled using the drill bar to enlarge the holes in the firewall to 3/16 on the new centerlines. Worked perfectly. Installed the Fuse Box. The left hand side bolts are in a flat area next to a rib and use new holes.