I used a grinder to get the u shape in the bolt heads, when you see it in person you'll get it. Also, ground some snug fitting washers, 5/16 fender washers, as you don't want all that pressure compressing right on the aluminum.
From here you can see the idea, and the stack. Bracket, axle flange, spacer, bearing cap. I used 3/8 x 2 grade 8 bolts.
