edit- if you don't shim it, it will probably hold zero just fine until you smack it really hard. It's a roll pin with an interference fit, but if you hit it hard enough it will move. The only fix for this is to make a shim in a metal of your choice and wedge it in there with the front bit before you hammer the roll pin through.
I shimmed the play out of it so it can't move.
edit- if you don't shim it, it will probably hold zero just fine until you smack it really hard. It's a roll pin with an interference fit, but if you hit it hard enough it will move. The only fix for this is to make a shim in a metal of your choice and wedge it in there with the front bit before you hammer the roll pin through.