Alex, redundancy is fine, but if the method of attachment is suspect then its pointless, because both wires will have equal possibility of failing at the same point.
Better one properly made connection than 2 dodgy ones!
Chances are the metal part is electroplated and you will have a hell of a job soldering to it.
Stay with the screw and add some non-permanent thread lock. (you may need to undo it at some point!)
If youre at Colechester come and find me and Ill take a look at it for you.