Renogy ANL fuse holder base

I am using a Renogy ANL fuse in my Solar Photovotaic installation. Their ANL fuses are rated for the amperage as well as the DC voltages that I need. I was surprised to see the back of the fuse holder has the bolt heads for the lug mounts exposed. I figured if mounted on metal...and you had a surge that would blow the fuse --- there MAY be a possibility of arcing from the bolt head to a metal surface. I made this mount to act as an additional insulator for mounting on metal. Afterwords...I