[Bruce_MO]

I just backed them up with a body dollie and hammer carefully on them until they're tight and uniformly "mashed". I can't say that any of them ended up loose that way; they all seemed to be pretty snug for me. I think if you grind the sheetmetal too thin to remove the orignal nut, then it'll be a lot more likely that the new one could be loose.

It seems to me that the originals must have been installed with some sort of press or pneumatic hammer fixture, as they always seem very uniform w/o the look of someone rapidly hammering on them. The "mashed" portion is always perfectly round and smooth in the ones I've looked at.