I thought about that as well but non of my bolts had the flats lined up exactly. I don’t think that when the cross holes are drilled they are in any particular position. I don’t remember who but someone on the forums had a supplier of rings with a 12 point pattern on the inside diameter that looked similar to a boxed end wrench. These rings would be placed over a bolt and welded all around. This would hold the bolt securely in place.
Well, after seeing this, the first thing I'm going to do is weld two strips of 1/8 steel to each side of the hole to hold the bolt from spinning once installed.