Paddy - not sure I believe your above statement.
As far as I knew a Group N disc had been heat treated and cycled over a standard disc so there for they have been burnt in. This is for where regulations state a non slotted or non grooved disc has to be fitted.
Either way I am still very happy with this set up and it remains unchanged.
If you don't need the abs ring - just pull it off and advertise it for sale. somebody will buy it I'm sure.