I wired in a Givi top box with additional LED tail and brake lights. Had to modify the Givi system as they don't do the rack connection for the XR. I'm not familiar with the Shad set up.
However, I had to install a Skene IQ-260 controller to overcome CanBus issues. It will likely throw a lamp error if you splice into the tail light (like mine did, I tried it first) due to the system sensing more current on the wire than is expected. The controller is tiny and easily tucks away under the seat and is easy to wire in (full instructions come with it). Cost me 98 U.S Dollars a couple of years ago, 33 of which was shipping. So about 75 quid all in.
It's available in the U.K through the "Adventure Bike Shop", but there was a delay at the time I wanted it and of course being the U.K; it was more expensive, so I ordered direct from Skene in the U.S.
