I didn't mount the bracket on the mirror frame itself, but below it on the arm. On my Velvac there's a small black plastic cover that can be removed to gain a bit of access. The hole was drilled so that I could get the small bolt inside with a serrated lock-washer and then attach the bracket underneath with a locking nut. Putting the nut on the outside would allow easier tightening in the future if needed, and applying a bit of Loctite on the threads as well for additional security. The positioning of the new mirror doesn't interfere at all with the Velvac.