The 1/2" doesn't fit the frame hole. I would need to get a die grinder and enlarge the hole. 1/2" is about 0.028" bigger than 12mm (12mm = 0.472"). The 1/2" bolt is still loose, but not as sloppy as 12mm. The other thing is that I can easily get the grade 8 SAE bolts (and have them already).