Wow 12mm that’s a lot - cheersA bit tight under the battery lead but just massage it up and gently slip the brace under. From memory they were 12mm but I also just shaved a smidge off the back of the brace where it contacts the K brace. Also check the proper torque the bolts need to be tightened to. I don’t remember exactly. The so called RHD adjusted braces are just ground off where I shaved it to go over the K brace. Good luck.