There is a little bit of play in the steering on my front right wheel. I've traced it back to a little bit of play in the in the spindle arm ball stud (I think that's what it's called?). Basically, if I tighten the castle nut pictured below to take out all the slop then the castles don't line up with the hole for the cotter pin. I've left it backed off enough such that I can get a cotter pin in it since I really don't want that nut backing off more while I'm driving. I don't really understand why it doesn't "just work", seems like all the geometry should be fixed by the parts so that it does "just work."
Should I shim it such that the castles line up, or just leave it alone, or?