He put some stupid little fairing on it for looks, it would cause him high speed wobbles in the turns and I'd pass him.
I don't think the XS1100 needed a stupid little fairing to make it all wobbly in turns Steve, they did that straight off the showroom floor!
Some "Bikini" fairings caused high speed wobbles though, the Suzuki GS1000S fairing was a classic example, that's why there were som many GS1000S fairings hanging in owners garages, (including mine) taking them off actually made them more stable. BMW's R90S fairing was a similar design, and sadly, had a similar effect, but BMW riders were either braver, or didn't ride as fast (my best guess) because they mostly kept them on.
What exacerbated the problem on the R90S was the fitment of the factory panniers, I had both the R90S fairing and Krauser panniers on my first R100RS, and it developed one hell of a "Tank Slapper" at around 100 MPH. The fix (for me at least) was not to ride at 100 MPH.............