Just had a look again and the centering of the rear brakes can definitely be improved... The right pad hits the rim first... and that is what is causing the wheel to be pushed 'off' its true alignment when the brakes are tightly closed.

It took me a long time to be happy with the centering of the front brakes but I have always been happy with rear brakes - should have checked more closely.

As I said before, its 1/8" movement at worst, so I'm thinking correct centering is at least best practice if not a complete remedy...