[Closed] Running 11 speed campag rear mech on 10 speed campag setup?

I have a centaur 10 speed mech (old style) and I have read that the spring in the early mechs was rather weak. I don't find the shifting very good and I can't deduce whether it is the front shifter that is playing up or whether it is the spring in the rear mech not being very strong. The shifting is not snappy when I change down.

I have changed cable inners and outers, but the shifting is always out and never stays true.

So I was wondering whether I can run an 11 speed rear mech on a 10 speed setup. Given there is no indexing on a rear mech I suspect it makes no difference?

Thanks