re: other option
those brembo calipers are available up the road (motomecca, guzzi place) at about £120, new. trouble is there are several different models that all look the same but with differing mounts etc.
as you have the same ineffective twin piston P9 brembo on the front of your mono as on my para, i am interested to know how it knows what sort of rear end is fitted & is able to adjust braking power accordingly. does it have a different disc/master cylinder?